Re: SWAPGEN
As one of the SWAPGEN authors, I've watched this discussion. I'd note that Barton's original statement stands, in the context in which he said it: VDISK has always provided better *performance* in every observed case. The concerns about using up real memory have never been supported by the data. The pathological cases of This guest runs away, real Swap DASD gives me a chance to control it are perfectly valid, but don't contradict the statement that VDISK is better *for performance*; rather, they support it. ...phsiii
Re: SWAPGEN
On Sat, May 2, 2009 at 12:46 PM, Phil Smith III li...@akphs.com wrote: The pathological cases of This guest runs away, real Swap DASD gives me a chance to control it are perfectly valid, but don't contradict the statement that VDISK is better *for performance*; rather, they support it. Let me show you the numbers on a beer coaster then... I worked with Terry on his setup and recommended that in this exceptional case it would make sense to put a gravel bed next to the road to slow down the penguin with no brakes It turns out their application had a bug/failure in that it had apparently an endless demand for memory in some situation. Since VDISK is fast, you can fill it up pretty quick - at 40 MB/s your 2G VDISK is full in a minute. But filling up the VDISK did not hurt z/VM, it just made Linux give up when it ran out of swap space. And that hurt their application (probably the ungraceful shutdown required journal recovery etc of a large disk, etc). If you do the math, you will see that a penguin with intention to kill itself could also fill a 2G real disk in 10 minutes or so. In this case that was enough because they were sitting next to it during the test. When you don't expect it to happen, you will not be there in time to rescue the penguin. So I conclude: when the memory requirements of the application exceed your planned capacity just a little (say less than the swap space you set up to support Linux memory over commit) then VDISK will do fine. It does not hurt z/VM and it avoids people complain about the sudden slowdown. When Linux needs way more than planned, it will fill up swap space (whether VDISK or real) and the Out-of-Memory Killer will stop vital processes during the crash. The only advantage of the real swap disk is that it postpones the moment of crash with an hour and costs more money. Not a hard choice for me. Tuning by opinion and fear rarely is cost-effective. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/
Re: SWAPGEN
Thanks Rob! Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov -Original Message- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Rob van der Heij Sent: Saturday, May 02, 2009 9:32 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN On Sat, May 2, 2009 at 12:46 PM, Phil Smith III li...@akphs.com wrote: The pathological cases of This guest runs away, real Swap DASD gives me a chance to control it are perfectly valid, but don't contradict the statement that VDISK is better *for performance*; rather, they support it. Let me show you the numbers on a beer coaster then... I worked with Terry on his setup and recommended that in this exceptional case it would make sense to put a gravel bed next to the road to slow down the penguin with no brakes It turns out their application had a bug/failure in that it had apparently an endless demand for memory in some situation. Since VDISK is fast, you can fill it up pretty quick - at 40 MB/s your 2G VDISK is full in a minute. But filling up the VDISK did not hurt z/VM, it just made Linux give up when it ran out of swap space. And that hurt their application (probably the ungraceful shutdown required journal recovery etc of a large disk, etc). If you do the math, you will see that a penguin with intention to kill itself could also fill a 2G real disk in 10 minutes or so. In this case that was enough because they were sitting next to it during the test. When you don't expect it to happen, you will not be there in time to rescue the penguin. So I conclude: when the memory requirements of the application exceed your planned capacity just a little (say less than the swap space you set up to support Linux memory over commit) then VDISK will do fine. It does not hurt z/VM and it avoids people complain about the sudden slowdown. When Linux needs way more than planned, it will fill up swap space (whether VDISK or real) and the Out-of-Memory Killer will stop vital processes during the crash. The only advantage of the real swap disk is that it postpones the moment of crash with an hour and costs more money. Not a hard choice for me. Tuning by opinion and fear rarely is cost-effective. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/
Re: SWAPGEN
Yep, rule of thumb as well as 98% of the time, vdisk for swap is the way to go. But there still is use for swap on real disk. One is to throttle the image, the other is to keep the max resident size down sufficiently enough to keep from impacting production systems by overloading the paging system. A lot can be done with the paging system, especially if you have the money. But for those of us that occasionally hit a paging cliff It would be better if there was a command to limit the amount of resident memory a guest could have. Something like your resident memory plus dataspace resident memory couldn't exceed 512 MB. When I think about what it would take to modify the paging subsystem, to prefer some users memory for pageouts, my brain starts hurting. Until then, swap on real disk can help reduce the problem. I got a request in from a Network guy that wants a Linux image to play around with. Initially some sort of network performance monitor. I won't have time to sit with him to keep the normal, I got a box that I'm the only user on, and it doesn't matter what I do mentality, so I do need to keep his resident size down. So, a couple vdisk swap disks, and a full 3390-3 real swap disk. If things go well, and his application is ready for prime time with his memory requirement really known, then swap disks will be redefined, without the real disk. There are always exceptions to the rule. But then, if I had the funds for a real performance monitor, I might be able to see a different solution. Right now, my alerts come in the form of the phone ringing. Of course, if I had more funds to buy more memory, I could create another LPAR and have these weird images in their own Linux farm. But that would then require me to dedicate real resources to a set of images that, on any given day, may never be used. Dedicate real memory vs dedicate real dasd. I have more dasd, for now. Tom Duerbusch THD Consulting Doug Shupe dsh...@bellsouth.net 4/29/2009 8:58 PM Scott you hit this one on the head! Penguins multiply rapidly, real memory tends to stay constant ($$$). Sure VM is Great at paging but, like you say, impacting all the Penguins? YMMV. Alerts are a must either way. When memory is at a premium, one v-disk and the rest real disk is the way to go. DASD is not 'that' slow anymore. Doug - Original Message - From: Scott Rohling To: IBMVM@LISTSERV.UARK.EDU Sent: Wednesday, April 29, 2009 18:13 Subject: Re: SWAPGEN Maybe -- but having a real disk (and setting an alert for that) helps isolate the issue to a single guest rather than affecting critical shared resources (in this case memory/paging) when a guest starts swapping more than normal or than it 'should'. I like the idea of having a 'failover' swap area on real disk -- whether you have a single VDISK or 2 prioritized ahead of it. I guess whether it's waste of resource depends on your POV.. But your point is taken.. Scott On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson bar...@vm1.velocity-software.com wrote: giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov//
Re: SWAPGEN
I'll shuddup now ;-)
I won't shuddup now! I suspect that some Blanket statements can turn
out to be Wet Blanket statements, ruining the party at some customer
sites, especially at new z/VM sites running POC's on hand-me-down machines
without a lot of real memory. As always: **It depends**!! {probably
(c) Bill Bitner}
Saying that all Linux swap disks should be defined as VDISKs does not take
into account different customer situations.
We happen to be blessed with lots of cheap(er), hand-me-down DASD from the
500lb Gorilla. OTOH, we _could_ be short of real memory (three large z/OS
guests in a virtual sysplex on that system).
Memory can be relatively expensive compared to relatively cheap DASD
(especially when one gets hand-me-downs).
Those secondary 'warning flag' VDISKs eat away at real, shared memory. If
you have a lot of Linux guests and not a lot of spare memory, aside from
making a call to delight your IBM hardware rep, you might want to
consider/total the memory cost of hundreds of small 'warning flag' swap
disks vs cheap disk. After all, they those swap disks are not supposed to
be used regularly. They are a warning that something else needs to be
evaluated and improved - maybe even making that servers swap VDISK larger!
More likely: trimming the default virtual storage size of the Linux guest
to something a lot smaller than the x86 folks say it MUST BE to function
properly.
But if you let a lot of servers fail over onto the warning flag swap disks
without doing anything about it, then someone could complain that all your
Linux guest performance is bad and abandon the migration to the mainframe.
Of course, a good performance monitor **and the skills to understand how
to use it and how to fix the problems** can alleviate that situation. That
assumes a lot, as many new z/VM customers (and many old ones, too!) don't
have those skills.
Summary: if you do use small failover swap space (a very good idea),
ensure that the warning is to pop up properly when they are used (as
Barton mentioned), test that warning by causing swap to the failover disk
(VDISK -or- real disk, regardless), and then react promptly when something
sets off the alert in production.
Mike Walter
Hewitt Associates
Disclaimer: What I -don't- know about performance fills lots of books...
literally!
Scott Rohling scott.rohl...@gmail.com
Sent by: The IBM z/VM Operating System IBMVM@LISTSERV.UARK.EDU
04/29/2009 08:51 PM
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Re: SWAPGEN
Right - I got that from Barton's post.
Consider that there are times when using a real disk might make sense ..
I'm just not big on blanket statements... Dedicating a resource is not
always a big waste and does not always benefit one to the detriment of the
rest. It's a balancing act and it takes all the tricks in the bag to keep
it from falling over. A real disk might make real sense with an
ill-behaved, unpredictable guest that is causing you swapping headaches.
That's what I was trying to point out..
Maybe I'd stay quiet if I saw some qualifiers like 'in general' when
people talk about BIG/REAL WASTE. Guidelines are nice, but I object to
them being presented as 'rules'.
I'll shuddup now ;-)
Scott
On Wed, Apr 29, 2009 at 6:16 PM, Rich Smrcina rsmrc...@wi.rr.com wrote:
The biggest benefit of z/VM is to virtualize resources as much as
possible. Dedicating a resource to a specific guest is a big waste and
benefits one to the detriment of all the rest. It would be much better to
allocate all virtual disk swap for the Linux guests, then allocate the
disk that would have been dedicated to swap as page space. That way
everyone wins.
Scott Rohling wrote:
Maybe -- but having a real disk (and setting an alert for that) helps
isolate the issue to a single guest rather than affecting critical shared
resources (in this case memory/paging) when a guest starts swapping more
than normal or than it 'should'.
I like the idea of having a 'failover' swap area on real disk -- whether
you have a single VDISK or 2 prioritized ahead of it. I guess whether
it's waste of resource depends on your POV.. But your point is taken..
Scott
On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson
bar...@vm1.velocity-software.com wrote:
giving real disks to swap is a real waste of resource. It is much better
to take the extra disk resource that you allocate but never want to use,
and assign it to z/VM paging to enhance your paging subsystem. Then
define two vdisks for swap, prioritize them, and set an alert when the 2nd
disk is being used.
Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR)
wrote:
Hi
I am using SWAPGEN to define by z/Linux VDISKS I also want to define a
real disk for swap. My question is can I use SWAPGEN to define a swap on
real DASD? If you have an example of the control card
Re: SWAPGEN
On Thu, Apr 30, 2009 at 6:21 PM, Rich Smrcina rsmrc...@wi.rr.com wrote: Both ESALPS and the Performance Toolkit will show that an unused Vdisk will use very little storage. Even if you do manage to start using it, after a certain amount of time it is likely to get paged out if unreferenced long enough. Barton has been presenting these topics at SHARE and WAVV for several years now, they should be well burned in... I can't speak for the other product, but you could be right ;-) The reason we tell you not to fill that second overflow VDISK is not because it would take up too much real memory, but because it will make things very slow even though you did not want it to. And because when VDISK gets paged out, you need twice the amount in page space. The overflow swap VDISK is like what normal swap is for Linux on other platforms: it's supposed not to get used unless the application went out of its mind or something like that. Assuming that not all servers go crazy at the same time, you can probably stand it reasonably well if you set up monitoring. When the workload slightly grew beyond expectation, it will drip into the 2nd VDISK only a little. That means it will take a while before it really takes up space, and you have time to handle it. Even when multiple servers seem to outgrow plan. As long as it is VDISK, people will not notice and you can plan for change. But when your 2nd VDISK is real disk, performance will be bad (even with only a little swapping) and big badges will prevent easy planning of the change. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/
Re: SWAPGEN
Hi Barton, Thanks for the information. I will have two VDISKs for my z/Linux guests already. I have found that when a z/Linux guest at least with my workload starts to use SWAP it plows through it in no time so the extra real disk for swap was to slow this down so that I could react quickly to head of off running out of SWAP. In some cases with some of my Oracle workload by the time I received the alert that the second VDISK was being used it would have already been used up. My paging subsystem is pretty robust as it stands and I do very little paging so far. Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov -Original Message- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Barton Robinson Sent: Wednesday, April 29, 2009 6:42 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov//
Re: SWAPGEN
Scott Wrote: A real disk might make real sense with an ill-behaved, unpredictable guest that is causing you swapping headaches. This is exactly why I want to allocate a real disk. I understand the theory behind what Rich and Barton are saying but in practice all workloads are not created equally. In my case I am planning for what I already know can happen (saw it during testing) so knowing this that is the only reason I am considering a real disk as a last precaution. Of course I am working with the application developers to enhance the efficiency of the application which is the REAL BANG FOR THE BUCK! Thanks to all for all of the responses it is much appreciated. Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov mailto:terry.mar...@cms.hhs.gov From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Scott Rohling Sent: Wednesday, April 29, 2009 9:51 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN Right - I got that from Barton's post. Consider that there are times when using a real disk might make sense .. I'm just not big on blanket statements... Dedicating a resource is not always a big waste and does not always benefit one to the detriment of the rest. It's a balancing act and it takes all the tricks in the bag to keep it from falling over. A real disk might make real sense with an ill-behaved, unpredictable guest that is causing you swapping headaches. That's what I was trying to point out.. Maybe I'd stay quiet if I saw some qualifiers like 'in general' when people talk about BIG/REAL WASTE. Guidelines are nice, but I object to them being presented as 'rules'. I'll shuddup now ;-) Scott On Wed, Apr 29, 2009 at 6:16 PM, Rich Smrcina rsmrc...@wi.rr.com wrote: The biggest benefit of z/VM is to virtualize resources as much as possible. Dedicating a resource to a specific guest is a big waste and benefits one to the detriment of all the rest. It would be much better to allocate all virtual disk swap for the Linux guests, then allocate the disk that would have been dedicated to swap as page space. That way everyone wins. Scott Rohling wrote: Maybe -- but having a real disk (and setting an alert for that) helps isolate the issue to a single guest rather than affecting critical shared resources (in this case memory/paging) when a guest starts swapping more than normal or than it 'should'. I like the idea of having a 'failover' swap area on real disk -- whether you have a single VDISK or 2 prioritized ahead of it. I guess whether it's waste of resource depends on your POV.. But your point is taken.. Scott On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson bar...@vm1.velocity-software.com wrote: giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov// -- Rich Smrcina
Re: SWAPGEN
make sure that your oracle SGA fits into your page cache. If it doesn't, that will make you swap. Your ORACLE DBA ABSOLUTELY must be in agreement on your configuration Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi Barton, Thanks for the information. I will have two VDISKs for my z/Linux guests already. I have found that when a z/Linux guest at least with my workload starts to use SWAP it plows through it in no time so the extra real disk for swap was to slow this down so that I could react quickly to head of off running out of SWAP. In some cases with some of my Oracle workload by the time I received the alert that the second VDISK was being used it would have already been used up. My paging subsystem is pretty robust as it stands and I do very little paging so far. Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov -Original Message- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Barton Robinson Sent: Wednesday, April 29, 2009 6:42 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov//
Re: SWAPGEN
Hi Marcy, Yes, I have played with that taking it from the default of 60 to 20 and it does help. I just have an oracle app that needs some work. Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov -Original Message- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Marcy Cortes Sent: Thursday, April 30, 2009 8:41 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN You might want to take a look at vm.swappiness setting. (see discussion here a few months ago). We found one of ours munched through it (not as fast as plowed) at a setting of 60 but not at a setting of 20 where it seemed to stay put. Marcy This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) Sent: Thursday, April 30, 2009 5:35 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] SWAPGEN Scott Wrote: A real disk might make real sense with an ill-behaved, unpredictable guest that is causing you swapping headaches. This is exactly why I want to allocate a real disk. I understand the theory behind what Rich and Barton are saying but in practice all workloads are not created equally. In my case I am planning for what I already know can happen (saw it during testing) so knowing this that is the only reason I am considering a real disk as a last precaution. Of course I am working with the application developers to enhance the efficiency of the application which is the REAL BANG FOR THE BUCK! Thanks to all for all of the responses it is much appreciated. Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 terry.mar...@cms.hhs.gov mailto:terry.mar...@cms.hhs.gov From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Scott Rohling Sent: Wednesday, April 29, 2009 9:51 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN Right - I got that from Barton's post. Consider that there are times when using a real disk might make sense .. I'm just not big on blanket statements... Dedicating a resource is not always a big waste and does not always benefit one to the detriment of the rest. It's a balancing act and it takes all the tricks in the bag to keep it from falling over. A real disk might make real sense with an ill-behaved, unpredictable guest that is causing you swapping headaches. That's what I was trying to point out.. Maybe I'd stay quiet if I saw some qualifiers like 'in general' when people talk about BIG/REAL WASTE. Guidelines are nice, but I object to them being presented as 'rules'. I'll shuddup now ;-) Scott On Wed, Apr 29, 2009 at 6:16 PM, Rich Smrcina rsmrc...@wi.rr.com wrote: The biggest benefit of z/VM is to virtualize resources as much as possible. Dedicating a resource to a specific guest is a big waste and benefits one to the detriment of all the rest. It would be much better to allocate all virtual disk swap for the Linux guests, then allocate the disk that would have been dedicated to swap as page space. That way everyone wins. Scott Rohling wrote: Maybe -- but having a real disk (and setting an alert for that) helps isolate the issue to a single guest rather than affecting critical shared resources (in this case memory/paging) when a guest starts swapping more than normal or than it 'should'. I like the idea of having a 'failover' swap area on real disk -- whether you have a single VDISK or 2 prioritized ahead of it. I guess whether it's waste of resource depends on your POV.. But your point is taken.. Scott On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson bar...@vm1.velocity-software.com wrote: giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card
Re: SWAPGEN
giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov//
Re: SWAPGEN
The biggest benefit of z/VM is to virtualize resources as much as possible. Dedicating a resource to a specific guest is a big waste and benefits one to the detriment of all the rest. It would be much better to allocate all virtual disk swap for the Linux guests, then allocate the disk that would have been dedicated to swap as page space. That way everyone wins. Scott Rohling wrote: Maybe -- but having a real disk (and setting an alert for that) helps isolate the issue to a single guest rather than affecting critical shared resources (in this case memory/paging) when a guest starts swapping more than normal or than it 'should'. I like the idea of having a 'failover' swap area on real disk -- whether you have a single VDISK or 2 prioritized ahead of it. I guess whether it's waste of resource depends on your POV.. But your point is taken.. Scott On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson bar...@vm1.velocity-software.com wrote: giving real disks to swap is a real waste of resource. It is much better to take the "extra disk resource" that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov// -- Rich Smrcina
Re: SWAPGEN
Scott you hit this one on the head! Penguins multiply rapidly, real memory tends to stay constant ($$$). Sure VM is Great at paging but, like you say, impacting all the Penguins? YMMV. Alerts are a must either way. When memory is at a premium, one v-disk and the rest real disk is the way to go. DASD is not 'that' slow anymore. Doug - Original Message - From: Scott Rohling To: IBMVM@LISTSERV.UARK.EDU Sent: Wednesday, April 29, 2009 18:13 Subject: Re: SWAPGEN Maybe -- but having a real disk (and setting an alert for that) helps isolate the issue to a single guest rather than affecting critical shared resources (in this case memory/paging) when a guest starts swapping more than normal or than it 'should'. I like the idea of having a 'failover' swap area on real disk -- whether you have a single VDISK or 2 prioritized ahead of it. I guess whether it's waste of resource depends on your POV.. But your point is taken.. Scott On Wed, Apr 29, 2009 at 4:42 PM, Barton Robinson bar...@vm1.velocity-software.com wrote: giving real disks to swap is a real waste of resource. It is much better to take the extra disk resource that you allocate but never want to use, and assign it to z/VM paging to enhance your paging subsystem. Then define two vdisks for swap, prioritize them, and set an alert when the 2nd disk is being used. Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? //Thank You,// //Terry Martin// //Lockheed Martin - Information Technology// //z/OS z/VM Systems - Performance and Tuning// //Cell - 443 632-4191// //Work - 410 786-0386// //terry.ma...@cms.hhs.gov mailto:terry.ma...@cms.hhs.gov//
Re: SWAPGEN
On 4/26/2009 at 10:44 PM, Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) terry.mar...@cms.hhs.gov wrote: I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? SWAPGEN only exists because VDISK are ephemeral. If you create one and use mkswap on it, there's no guarantee that swap signature will be there the next time the Linux system gets rebooted, because the guest may have been logged off before being rebooted. Rather than alter each Linux guest's startup scripts, SWAPGEN just makes it appear as though the VDISK never went away and came back again. Real disks don't have that problem. So, just give the Linux system the disk, bring it online, create a partition on it, use mkswap to turn it into a swap device, and then swap on to activate it. Update /etc/fstab to make the change permanent and you're done. Well, re-run mkinitrd and zipl so that the DASD volume will come back next time also. Mark Post
Re: SWAPGEN
On Apr 26, 2009, at 9:44 PM, Martin, Terry R. (LOCKHEED MARTIN Performance Engineering/CTR) (CTR) wrote: Hi I am using SWAPGEN to define by z/Linux VDISKS I also want to define a real disk for swap. My question is can I use SWAPGEN to define a swap on real DASD? If you have an example of the control card syntax to accomplish this that would be great? Why bother? Since real DASD is persistent, once you make a swap disk in Linux the first time, you just keep it around. The reason for SWAPGEN is that VDISK goes away on logout, and it was a pain to modify the boot process to add the swap signature before a swapon -a is done. Adam
Re: SWAPGEN not working for FBA
On Nov 7, 2008, at 4:30 PM, Martin, Terry R. (CMS/CTR) (CTR) wrote: Hi I am trying to use the SWAPGEN EXEC to create a FBA SWAP file by adding it to the PROFILE EXEC of the Linux guest. However it seems to keep taking the default of DIAG. Since I do not have the DIAG drivers on my RedHat REL4 guest I need to do FBA. Here is he syntax I am using: 'SWAPGEN 900 524288 FBA' I am tracing the EXEC now to see if I spot something. BTW I do have the RXDASD MODULE on the guest. This module is required for FBA swap. Does anyone have any ideas about this? SWAPGEN 900 524288 ( FBA It's an option. It comes after an open-paren. However, I think the FBA driver will actually work with a CMS- formatted disk and partition 1 of the device (rather than the raw device) if you leave DIAG off. Adam
Re: SWAPGEN not working for FBA
On 11/7/2008 at 5:30 PM, Martin, Terry R. (CMS/CTR) (CTR) [EMAIL PROTECTED] wrote: -snip- 'SWAPGEN 900 524288 FBA' Have you tried 'SWAPGEN 900 524288 ( FBA' ?? Mark Post
Re: SWAPGEN not working for FBA
It worked by specifying (FBA. Sorry for missing this in the HELP doc, went right by it! Thank You, Terry Martin Lockheed Martin - Information Technology z/OS z/VM Systems - Performance and Tuning Cell - 443 632-4191 Work - 410 786-0386 [EMAIL PROTECTED] From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Adam Thornton Sent: Friday, November 07, 2008 5:39 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN not working for FBA On Nov 7, 2008, at 4:30 PM, Martin, Terry R. (CMS/CTR) (CTR) wrote: Hi I am trying to use the SWAPGEN EXEC to create a FBA SWAP file by adding it to the PROFILE EXEC of the Linux guest. However it seems to keep taking the default of DIAG. Since I do not have the DIAG drivers on my RedHat REL4 guest I need to do FBA. Here is he syntax I am using: 'SWAPGEN 900 524288 FBA' I am tracing the EXEC now to see if I spot something. BTW I do have the RXDASD MODULE on the guest. This module is required for FBA swap. Does anyone have any ideas about this? SWAPGEN 900 524288 ( FBA It's an option. It comes after an open-paren. However, I think the FBA driver will actually work with a CMS-formatted disk and partition 1 of the device (rather than the raw device) if you leave DIAG off. Adam
Re: SWAPGEN EXEC
On Aug 7, 2008, at 4:28 AM, Berry van Sleeuwen wrote: Hello List, The past day I have tried to get the new version of SWAPGEN into my VM but no success so far. I have tried every way I can do a filetransfer but every time I end up in a file I can't use on VM. Can anyone send me the VMARC-ed version of the current SWAPGEN so I can continue? I do have the old version here but there seemds to be a problem with my VDISK swap so I'd like to try the newer version. (TIA) It's unlikely to helpthe recent changes are pretty minor. Nevertheless, the VMARC of the new version is now available at: http://download.sinenomine.net/swapgen/ BTW, when I look at the mailable I see the filelist of the included files. The RXDASD MODULE in mailable archive looks like to be from 3/15/04. I too have a RXDASD but that one is dated 18/11/95 and that is also the one from the IBM VM downloads. Is this RXDASD a different version or are they the same? Probably the same. I just wasn't careful about preserving the timestamp, but it just comes from the VM Downloads page. I've looked into the comments made here in June, and I have to agree with the comments Adam made (to go back to the VMARC format). IIRC, VMARC was recommended to use because of the fact that ASCII to EBCDIC translations vary among the various file tranfer methods. (Either FTP or IND$.) So by replacing VMARC with MAILABLE to avoid the need for some extra tool and/or to overcome less than default record formats, the transfer now relies on the fact of how your method of transferring files will handle ASCII to EBCDIC translation. IMHO this is much harder to solve than a faulty recordformat because the file itself will be altered by the transfer. At least with VMARC or CMS packed I know what recordformat it should be (either Fixed 80 or 1024) and can FBLOCK it after transfer. And because these files must be transferred in binary the file itself should not change by the transferprocess. Regards, Berry. Also note that Leland Lucius has written VMA, which is a portable utility to do vmarc manipulation. http://www.homerow.net/zvm/vma.htm This is handy if, for instance, you just want to extract the docs from a package and read them on the desktop system of your choice. Adam
Re: SWAPGEN EXEC
Hi, Berry. Adam Thornton wrote: On Aug 7, 2008, at 4:28 AM, Berry van Sleeuwen wrote: Hello List, The past day I have tried to get the new version of SWAPGEN into my VM but no success so far. I have tried every way I can do a filetransfer but every time I end up in a file I can't use on VM. Can anyone send me the VMARC-ed version of the current SWAPGEN so I can continue? I do have the old version here but there seemds to be a problem with my VDISK swap so I'd like to try the newer version. (TIA) What sort of problems are you having with SWAPGEN? -- DJ V/Soft z/VM and mainframe Linux expertise, training, consulting, and software development www.vsoft-software.com
Re: SWAPGEN EXEC
Hi Dave, The SWAPGEN creates the VDISK and the zLinux does accept the disk. But swap is not activated on the disk. To activate the swap I have to issue a mkswap before swapon. And after booting the guest it must be done again. I don't know if it is a problem with swapgen, with linux or some fstab issue. So before troubleshouting, I want to replace the current swapgen with the newest one and then test to see if it helps. I noticed that the vdisk in linux is reported by /dev/dasdk and a partition on /dev/dask1. But from the docs I understand that the disk in FBA should be used as /dev/dasdk and not dasdk1. Quite strange, we already have some linux images with a vdisk swap and nobody has complained about the swapdisk. Thanks for the swapgen file. Tomorrow I'll test it with this one. Regards, Berry. Dave Jones schreef: Hi, Berry. Adam Thornton wrote: On Aug 7, 2008, at 4:28 AM, Berry van Sleeuwen wrote: Hello List, The past day I have tried to get the new version of SWAPGEN into my VM but no success so far. I have tried every way I can do a filetransfer but every time I end up in a file I can't use on VM. Can anyone send me the VMARC-ed version of the current SWAPGEN so I can continue? I do have the old version here but there seemds to be a problem with my VDISK swap so I'd like to try the newer version. (TIA) What sort of problems are you having with SWAPGEN?
Re: SWAPGEN EXEC
Hello Adam, Ah, nice. Both versions are available now. Thanks. I have the vma-package. Indeed very nice and I use it very much. Regards, Berry. Adam Thornton schreef: On Aug 7, 2008, at 4:28 AM, Berry van Sleeuwen wrote: Hello List, The past day I have tried to get the new version of SWAPGEN into my VM but no success so far. I have tried every way I can do a filetransfer but every time I end up in a file I can't use on VM. Can anyone send me the VMARC-ed version of the current SWAPGEN so I can continue? I do have the old version here but there seemds to be a problem with my VDISK swap so I'd like to try the newer version. (TIA) It's unlikely to helpthe recent changes are pretty minor. Nevertheless, the VMARC of the new version is now available at: http://download.sinenomine.net/swapgen/ BTW, when I look at the mailable I see the filelist of the included files. The RXDASD MODULE in mailable archive looks like to be from 3/15/04. I too have a RXDASD but that one is dated 18/11/95 and that is also the one from the IBM VM downloads. Is this RXDASD a different version or are they the same? Probably the same. I just wasn't careful about preserving the timestamp, but it just comes from the VM Downloads page. I've looked into the comments made here in June, and I have to agree with the comments Adam made (to go back to the VMARC format). IIRC, VMARC was recommended to use because of the fact that ASCII to EBCDIC translations vary among the various file tranfer methods. (Either FTP or IND$.) So by replacing VMARC with MAILABLE to avoid the need for some extra tool and/or to overcome less than default record formats, the transfer now relies on the fact of how your method of transferring files will handle ASCII to EBCDIC translation. IMHO this is much harder to solve than a faulty recordformat because the file itself will be altered by the transfer. At least with VMARC or CMS packed I know what recordformat it should be (either Fixed 80 or 1024) and can FBLOCK it after transfer. And because these files must be transferred in binary the file itself should not change by the transferprocess. Regards, Berry. Also note that Leland Lucius has written VMA, which is a portable utility to do vmarc manipulation. http://www.homerow.net/zvm/vma.htm This is handy if, for instance, you just want to extract the docs from a package and read them on the desktop system of your choice. Adam
Re: SWAPGEN EXEC
Rob van der Heij [EMAIL PROTECTED] wrote: I am concerned about the approach of teaching adults to download and just run it to see what happens That's one of the aspects that distinguishes us from the folks who close their eyes and do Next, next, finish and end up re-install their operating system on a regular basis after a number of those actions. My preference is to use a familiar tool (like VMARC) to review what's in the archive before I unpack it. And when I forget, I can at least use it to get a list of the files it installed and use that to manage the package. Transfer of a file in binary is not harder than transfer in text mode - you just have to remember doing it right in both cases. Accidental damage during transfer of a self-expanding program is most likely to make it fail in a visible manner. Deliberate modification of the code would be a concern. Somehow it does not make sense to me to ship the packaging tools with each package. A self-extracting MAILABLE does NOT extract just by invoking itself -- when you invoke it, it tells you what's in it, same as a VMARC LIST. You have to say EXTRACT to extract it. I don't see how this is fundamentally different for the paranoid: Here's a VMARC of a nice EXEC I wrote called CHRISTMA, that shows you a pretty picture of a tree (or Here's a VMARC of a new version of VMARC, no, really, it isn't malware, honest, would I lie to you?). The problem with VMARC is that folks have to get VMARC itself. So that's an extra step, and one that can apparently be daunting for those with no experience transferring files across platforms (proof: if folks have trouble getting a flat, plaintext MAILABLE, you can be they'll have trouble getting a specific-format, binary VMARC). Transferring in binary *in a specific format* (F 80 in the case of a VMARC, F 1024 in the case of a COPYFILE (PACKed copy of VMARC MODULE) IS harder than plaintext, because different clients handle blocking/LRECL differently. This is the raison d'etre of MAILABLE. The truly paranoid can get a known good copy of MAILABLE and use *that* to extract MAILABLEs: MAILABLE some mailable a (LIST MAILABLE some mailable a (EXTRACT will both work on a self-extracting MAILABLE (it's smart enough to skip the Rexx code that's been prepended). So one conclusion from all this is that the biggest problem with MAILABLE is a lack of documentation discussing these issues. Which I'll fix soon, of course. And I'll include a discussion of LF vs CRLF, since that's been a problem for some people. Other suggestions welcome, of course... ...phsiii
Re: SWAPGEN EXEC
Thanks Fernando and DavidDave Jones sent me a VMARC version of SWAPGE N and it is working fine. To David Boyes :I tried what you suggested but when I Downloaded it to my PC then VM the file got mangled. I tried every possible way...maybe there i s something wrong on my PC, anyway am now working so thanks again.
Re: SWAPGEN EXEC
When you downloaded the MAILABLE file to your PC and then to VM, did you transfer the file as a TEXT file? A MAILABLE file is intended to survive going between different systems and arrive in a format that will unpack cleanly. George Shedlock Jr AEGON Information Technology AEGON USA 502-560-3541 -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Dave de Noronha Sent: Thursday, June 19, 2008 2:14 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: SWAPGEN EXEC Thanks Fernando and DavidDave Jones sent me a VMARC version of SWAPGE= N and it is working fine. To David Boyes :I tried what you suggested but when I Downloaded it to my= PC then VM the file got mangled. I tried every possible way...maybe there i= s something wrong on my PC, anyway am now working so thanks again.
Re: SWAPGEN EXEC
Dave_de_Noronha wrote: I am trying to download the SWAPGEN EXEC from the Sine Nomine website and cannot get it in a format we can use. I do not understand why it is in Mailable format. Can anyone please tell me how to do it or, if possible send me the code What problem are you having? The point of MAILABLE is to package multiple files, preserve timestamps, and be easy to extract without requiring extra tools (such as VMARC). I'm always interested in understanding what pitfalls await... ...phsiii
Re: SWAPGEN EXEC
What problem are you having? It would be nice to have some cookbook-style steps of how to use SWAPGEN on the Web site. On http://www.sinenomine.net/products/vm/swapgen the only instructions I see are: The VMARC file contains the updates to the module and control files, the EXEC, the RXDASD MODULE (for FBA mode), and the CMS HELP file. without requiring extra tools (such as VMARC). Oh wait a minute, is it a VMARC file or a MAILABLE file? And how does one work with MAILABLE files? Thanks. Mike MacIsaac [EMAIL PROTECTED] (845) 433-7061
Re: SWAPGEN EXEC
On Thu, Jun 19, 2008 at 4:26 PM, Michael MacIsaac [EMAIL PROTECTED] wrote: What problem are you having? I am concerned about the approach of teaching adults to download and just run it to see what happens That's one of the aspects that distinguishes us from the folks who close their eyes and do Next, next, finish and end up re-install their operating system on a regular basis after a number of those actions. My preference is to use a familiar tool (like VMARC) to review what's in the archive before I unpack it. And when I forget, I can at least use it to get a list of the files it installed and use that to manage the package. Transfer of a file in binary is not harder than transfer in text mode - you just have to remember doing it right in both cases. Accidental damage during transfer of a self-expanding program is most likely to make it fail in a visible manner. Deliberate modification of the code would be a concern. Somehow it does not make sense to me to ship the packaging tools with each package. Rob (from a comfortable place at the gallery, frowning at what grew out of the 10 lines posted a few years ago)
Re: SWAPGEN EXEC
On Jun 19, 2008, at 9:00 AM, Phil Smith III wrote: Dave_de_Noronha wrote: I am trying to download the SWAPGEN EXEC from the Sine Nomine website and cannot get it in a format we can use. I do not understand why it is in Mailable format. Can anyone please tell me how to do it or, if possible send me the code What problem are you having? The point of MAILABLE is to package multiple files, preserve timestamps, and be easy to extract without requiring extra tools (such as VMARC). I'm always interested in understanding what pitfalls await... Well, last time it was a difference between PC and Unix line endings. I'm very tempted to go back to VMARC and say download as binary, reblock to FIX 80, unpack with VMARC. Go get VMARC if you don't have it, because we didn't have these problems reported before we went to MAILABLE for the download. But there's a lot of confusion with MAILABLE. Adam
Re: SWAPGEN EXEC
It's in MAILABLE format because it's actually a package of several files. Download the MAILABLE file to your VM system. RENAME the file to SWPG0803 EXEC and run it to extract the 11 encoded files. Use and enjoy.
