Re: RAM question for everyone!
On Fri, 2009-01-23 at 16:46 +, Bryn M. Reeves wrote: Gilboa Davara wrote: Yeah, but this problem can more-or-less be avoided by lowering /proc/sys/vm/swappiness. Sure, that will make the VM more likely to evict pagecache data than anonymous pages when it's trying to free pages. I haven't tested this to any real degree on my desktop boxes (as I don't really suffer too much from this with the setups that I run), does it give a significant benefit for this case? I can imagine it would given that systems where I have seen problems like this have tended to seem a bit cache-heavy, but testing results are always good to hear. Regards, Bryn. To be honest, now-days, I rarely tweak the swappiness value. While it was required on a 32bit machine with 2GB of memory, the default value works just fine on most 64bit workstation (and server) I use these-days. Even on servers with relatively long up times (4 months), I rarely see more than 100-200MB of swap being used. * - Gilboa * Unless something goes horribly wrong (mostly due to admin error), in which case, I'm glad that I had a lot of swap space ready just in case... -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
RAM question for everyone!
I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this app do? What worries me with that is no swap space. With an app that takes up that much RAM, I'd be wanting some swap space. But, as I said a lot depends on what the application does. If the app doesn't do any reads/writes from disk, or if there is no possible growth of the app beyond 8GB, then having no swap would probably be okay. But you have to keep in mind that the app isn't the only thing running, you have other kernel services and system services which also take up RAM. If I were you, I'd go with more than 10GB and add a couple GB swap space, just to be safe. -- Frustra laborant quotquot se calculationibus fatigant pro inventione quadraturae circuli Mark Haney Sr. Systems Administrator ERC Broadband (828) 350-2415 Call (866) ERC-7110 for after hours support -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? You don't mention the platform, but can we assume it's 64-bit (x86_64?) from the fact that the app is using 8G of ram? Regards, Bryn. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Bryn M. Reeves wrote: Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. True, but the assumption was 64-bit since he says the app uses 8GB RAM. -- Frustra laborant quotquot se calculationibus fatigant pro inventione quadraturae circuli Mark Haney Sr. Systems Administrator ERC Broadband (828) 350-2415 Call (866) ERC-7110 for after hours support -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 15:43 +, Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan Of the top of my head: Memory: If the machine is designed to run a single application and -nothing- else, 9-10GB will do. However, if you plan to have, say local and remote X, VNC, I'd add ~2GB the mix. Swap: Always setup some kind of swap - at-least 1-2GB. Disk space is cheap, but if you somehow miscalculate the amount of memory your application needs - even by 5% - the lack of available memory will trigger the OOM killer. (Which tends to produce problematic results... such as killing sshd and getties [happened to me once...]) In general, I usually setup 2-4GB swap on desktops, and 8GB of workstations/servers. E.g. I'm typing this on a dual Xeon workstation with 8GB of memory and 8GB of swap and less than 71M of swap is being used. - Gilboa -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 4:07 PM, Mark Haney mha...@ercbroadband.org wrote: Bryn M. Reeves wrote: Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. True, but the assumption was 64-bit since he says the app uses 8GB RAM. -- Thanks for the info, but if my only reads from disk and will not grow beyond 8GB is it true to say that I have no need for swap space if I install 10GB or more of RAM? Dan -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 7:43 AM, Dan Track dan.tr...@gmail.com wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I'm really curious. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
RE: RAM question for everyone!
Hi there -- One question that needs to be answered is whether or not the operating system in question is 32-bit or 64-bit architecture. The 32-bit architecture has a 'glass ceiling' limit of up to 4 gigabytes of RAM that it can access. The same is not true for 64-bit architecture. Once you have the answer to the above, you can make a better decision on the RAM package. -Original Message- From: fedora-list-boun...@redhat.com [mailto:fedora-list-boun...@redhat.com] On Behalf Of Dan Track Sent: Friday, January 23, 2009 10:43 AM To: Community assistance, encouragement,and advice for using Fedora. Subject: RAM question for everyone! I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Original Message Subject: Re: RAM question for everyone! From: Alan Evans ame.fed...@gmail.com To: Community assistance, encouragement, and advice for using Fedora. fedora-list@redhat.com Date: 01/23/2009 10:19 AM This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Alan Evans wrote: On Fri, Jan 23, 2009 at 7:43 AM, Dan Track dan.tr...@gmail.com wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I think many people aren't as concerned about sacrificing a bit of disk space as much as they are concerned about the performance impacts when the system begins to use the swap, especially for desktops. Linux will attempt to move old data that has not been referenced for some time out to the swap device even when there is relatively little pressure to do so. This is generally a win since we are better utilising the physical memory of the system (storing more frequently/recently used data in it) but it may lead to nasty delays when the swapped-out data is needed again. This is more of a problem today than 15 years ago because of the ever widening gulf between main memory speeds and (HD based) mass storage speeds (or at least, seek times). As an example, try opening something in OpenOffice and then minimizing it for a week. Even if the box was fairly quiet for that period, chances are that much of OO's address space is now swapped out. Clicking the window in the task bar will cause the system to churn for a few seconds or more before the app returns to a usable state. Regards, Bryn. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 10:24 -0600, Michael Cronenworth wrote: Original Message Subject: Re: RAM question for everyone! From: Alan Evans ame.fed...@gmail.com To: Community assistance, encouragement, and advice for using Fedora. fedora-list@redhat.com Date: 01/23/2009 10:19 AM This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. In which case the real question is not how much swap do I need? but how much RAM do I need to avoid swapping?. poc -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 16:26 +, Bryn M. Reeves wrote: Alan Evans wrote: On Fri, Jan 23, 2009 at 7:43 AM, Dan Track dan.tr...@gmail.com wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I think many people aren't as concerned about sacrificing a bit of disk space as much as they are concerned about the performance impacts when the system begins to use the swap, especially for desktops. Linux will attempt to move old data that has not been referenced for some time out to the swap device even when there is relatively little pressure to do so. This is generally a win since we are better utilising the physical memory of the system (storing more frequently/recently used data in it) but it may lead to nasty delays when the swapped-out data is needed again. This is more of a problem today than 15 years ago because of the ever widening gulf between main memory speeds and (HD based) mass storage speeds (or at least, seek times). As an example, try opening something in OpenOffice and then minimizing it for a week. Even if the box was fairly quiet for that period, chances are that much of OO's address space is now swapped out. Clicking the window in the task bar will cause the system to churn for a few seconds or more before the app returns to a usable state. Regards, Bryn. Yeah, but this problem can more-or-less be avoided by lowering /proc/sys/vm/swappiness. - Gilboa -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Gilboa Davara wrote: Yeah, but this problem can more-or-less be avoided by lowering /proc/sys/vm/swappiness. Sure, that will make the VM more likely to evict pagecache data than anonymous pages when it's trying to free pages. I haven't tested this to any real degree on my desktop boxes (as I don't really suffer too much from this with the setups that I run), does it give a significant benefit for this case? I can imagine it would given that systems where I have seen problems like this have tended to seem a bit cache-heavy, but testing results are always good to hear. Regards, Bryn. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 4:25 PM, Patrick O'Callaghan pocallag...@gmail.com wrote: On Fri, 2009-01-23 at 10:24 -0600, Michael Cronenworth wrote: Original Message Subject: Re: RAM question for everyone! From: Alan Evans ame.fed...@gmail.com To: Community assistance, encouragement, and advice for using Fedora. fedora-list@redhat.com Date: 01/23/2009 10:19 AM This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. In which case the real question is not how much swap do I need? but how much RAM do I need to avoid swapping?. poc Hi All, This wasn't addressed to any paricular architecture, it was more of a query. Why do I even need swap or a large disk if all my app does is read a few pieces from a database on disk and if I load the database into RAM is there ever a need to look at the hardisk, given that the database never changes. Thanks Dan -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 8:24 AM, Michael Cronenworth wrote: SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. Of course I'm perfectly aware that RAM is much faster than hard drive storage. The OP asked how much memory he needed so he didn't have to configure any swap. He even mentioned that the server's hard drive was small as one of the reasons for not wanting swap. My machines, both desktop and server, *all* have swap, even if I don't expect to ever need it. Normally, the swap usage is zero, which is what I want. But there have been instances that the presence of the rarely-touched swap space has saved my ass. It just seemed like a silly cost-saving technique. He was willing to sink hundreds of dollars on a huge amount of RAM, but was unwilling to devote an extra 10-20 dollars on a hard drive big enough to provide swap space. (Apologies if other currencies are involved.) I understand not wanting to swap. I don't understand not want swap available at all. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Michael Cronenworth wrote: I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. No, you don't want to /have/ to use swap in normal production (this means having enough RAM). You still want to have swap for unforeseen circumstances. Matt Flaschen -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Kaplan, Andrew H. wrote: Hi there -- One question that needs to be answered is whether or not the operating system in question is 32-bit or 64-bit architecture. The 32-bit architecture has a 'glass ceiling' limit of up to 4 gigabytes of RAM that it can access. It's more of a ice ceiling. With Physical Address Extension, you can bring it up to 4 GB /per process/, and 64 GB total, but it's typically not worth the hassle. However, the OP mentioned 8 GB for one app, so I assume it's 64-bit. Matt Flaschen -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 11:07 -0500, Mark Haney wrote: Bryn M. Reeves wrote: Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. True, but the assumption was 64-bit since he says the app uses 8GB RAM. I guess I do not comprehend the issue of more memory stressing low memory? I know that a 32 bit system is constrained in addressing to something like 4G, due to the intel addressing architecture, and 32 bit constraint, so applications were developed to go beyond that. But given that the system maps the logical memory to physical memory, and some can do this via hardware, how does adding more memory add more stress? If the system is running the application now, the basic change is reducing swapping to disk, is it not? Regards, Les H -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Les wrote: On Fri, 2009-01-23 at 11:07 -0500, Mark Haney wrote: I guess I do not comprehend the issue of more memory stressing low memory? I know that a 32 bit system is constrained in addressing to something like 4G, due to the intel addressing architecture, and 32 bit constraint, so applications were developed to go beyond that. But given that the system maps the logical memory to physical memory, and some can do this via hardware, how does adding more memory add more stress? If the system is running the application now, the basic change is reducing swapping to disk, is it not? Regards, Les H While the 32bit machine can physically use more then 4G of memory the I/O hardware can only move stuff in and out of the first 4G. Therefore any I/O that a process in high memory is doing has to be bounced/buffered through somewhere under the 4G mark. The CPU ends up doing all the copying and the memory is now committed to I/O buffering rather than programs or data. Jeff Voskamp Feel free to correct me if I'm wrong (and I know you will). -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Dan Track wrote: On Fri, Jan 23, 2009 at 4:07 PM, Mark Haney mha...@ercbroadband.org wrote: Bryn M. Reeves wrote: Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. True, but the assumption was 64-bit since he says the app uses 8GB RAM. -- Thanks for the info, but if my only reads from disk and will not grow beyond 8GB is it true to say that I have no need for swap space if I install 10GB or more of RAM? Dan This is an interesting discussion. From what I read, I would put in at least 10GB of ram in what ever arrangement the system will allow. I would also create a swap partition of 4-10G and enable it. If you don't need it then you can turn it off. If it doesn't affect performance, then you can leave it on. Swap will only be used if it needs to be. And if the server is critical, then at least there is a buffer if there is a problem. I have 8 Gig ram and an 8 Gig swap. Some times I work with 6 and 8 Gig graphic files so the swap comes into play. If I don't work with large files for some time, I don't see any swap usage at all. I have never done it but I understand that you can create a swap file and use that so you could get by without creating a swap partition. It is a simple process of turning it on or off. -- Robin Laing -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan I've said it before, and I'll say it again: you should always* have a little bit of swap space. Yes, things get slower when you start swapping, but Linux, unlike Windows, doesn't swap when it doesn't need to. If you have swap space, then as soon as you start using it, the performance hit to the app that's dirtying pages like mad gives the kernel more opportunity to free up other memory, reducing the risk of OOM-kills or kernel OOM panics. You don't need a lot, and in fact I generally don't recommend having a lot these days, but you really should have some. -- Chris *There are certain carefully-tuned exceptions to this, but if you have to ask, they don't apply to you. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 16:16 +, Dan Track wrote: On Fri, Jan 23, 2009 at 4:07 PM, Mark Haney mha...@ercbroadband.org wrote: Bryn M. Reeves wrote: Mark Haney wrote: Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? Your thoughts are appreciated. Thanks Dan With RAM, the more the merrier. I guess the question is, what does this Unless you're on a 32-bit system in which case more RAM can make you much less merrier since the mere addition of the memory causes more pressure on the already constrained lowmem available on these platforms. Regards, Bryn. True, but the assumption was 64-bit since he says the app uses 8GB RAM. -- Thanks for the info, but if my only reads from disk and will not grow beyond 8GB is it true to say that I have no need for swap space if I install 10GB or more of RAM? Dan Unless you like to spend money you should have a little swap space. As someone else pointed out there are other things running besides you program. Although if you run the free program you will find that in most cases swap is not used much unless really necessary under Linux. -- === Only the hypocrite is really rotten to the core. -- Hannah Arendt === Aaron Konstam telephone: (210) 656-0355 e-mail: akons...@sbcglobal.net -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, 2009-01-23 at 13:13 -0700, Robin Laing wrote: Some times I work with 6 and 8 Gig graphic files so the swap comes into play. That piqued my interest. If I may ask, what are you doing? 3D rendering of the planet Earth in 1 metre resolution? -- [...@localhost ~]$ uname -r 2.6.27.9-73.fc9.i686 Don't send private replies to my address, the mailbox is ignored. I read messages from the public lists. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
Dan Track wrote: I was recently asked a question about how much RAM should there be within a server given that the APP uses 8GB of Memory, should I buy 10Gig of memory and have a small harddrive and no swap space? Would this configuration allow everything in my OS to run from RAM and not from swap? If this is the case then there's no need to ever create swap, is there?!? We just discussed this in the Ideal swap partition size thread. If your application is 8GB, you need at least 16GB of address space in case the server attempts to call an external program. When it does so, it will call fork(). While fork() will not copy all of the pages of a process under Linux, you do generally need to have the space available. If you're going to run an 8GB database server, with 10GB of RAM, I would strongly recommend at least 10GB swap space. You won't use it, but the system won't work reliably if it's missing. -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 04:54:24PM +, Dan Track wrote: On Fri, Jan 23, 2009 at 4:25 PM, Patrick O'Callaghan . I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. In which case the real question is not how much swap do I need? but how much RAM do I need to avoid swapping?. poc Hi All, This wasn't addressed to any paricular architecture, it was more of a query. Why do I even need swap or a large disk if all my app does is read a few pieces from a database on disk and if I load the database into RAM is there ever a need to look at the hardisk, given that the database never changes. The most missed VM issue in discussing swap space is the classic fork() -- exec(something_smaller) sequence. If you have a 10GB application that wants to print it will commonly do a fork() which will cause the VM system to make reservations for a second copy (10GBx2=20GB). For the short time up to the exec(and_now_print) the system must convince itself that the fork() will succeed. i.e. the sum of RAM and swap needs to be big enough for both copies to survive copy on write VM activity. In the normal case there is almost no copy on write so the swap pages on disk are never needed except to satisfy the book keeping. Like the banking industry the kernel can have a bit set to trust me and blindly extend credit. While vm.overcommit_memory exists it can set the stage for a system VM page credit crunch and crash (not just a slow down). Another good reason for swap use is 'job control' on servers. Almost no one does this any more but it can make sense to have a set of programs running such that running one at a time is the only way the system can avoid thrashing. A batch system can signal them to sleep or continue and time slice them on tens of minute basis rather than 100 slices per second. The bash man pages mentions job control in passing see this stuff: selectively stop distributed prime factor programs can watch this in action. Sadly this 'VM' issue, so close to financial credit activity, is simply not understood. I suspect if it was understood the world credit markets would be in less trouble. Yet, it can be taught with 3x5 cards in primary schools. Yea modeled with 3x5 cards and Monopoly money in a business meeting. Same for mutual exclusion locks and queues most companies (and families) operate on a 'race' and spend it first greedy model. -- Regards, T o m M i t c h e l l -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
Re: RAM question for everyone!
On Fri, Jan 23, 2009 at 11:55:20AM -0430, Patrick O'Callaghan wrote: On Fri, 2009-01-23 at 10:24 -0600, Michael Cronenworth wrote: Original Message Subject: Re: RAM question for everyone! From: Alan Evans ame.fed...@gmail.com To: Community assistance, encouragement, and advice for using Fedora. fedora-list@redhat.com Date: 01/23/2009 10:19 AM This question, along with other recent discussion about swap, leads me to ask a question in response: Why is everyone so concerned about how to get away without swap? Hard drives are cheap. Why does your server with potentially 10GB (!!!) of RAM have a hard drive so small that you can't sacrifice a few GB for swap? I'm really curious. SATA Hard drive speeds - 70 megs to 150 megs a second unless you're RAIDing DDR2 RAM speeds - 6000 megs a second and up. If performance is a key issue, which I'm sure it is, you don't want swap. In which case the real question is not how much swap do I need? but how much RAM do I need to avoid swapping?. My philosophy on that question is: Figure the worst-case max amount you'll ever need then double it. At least. If not triple. -- --- .Fred Smith / ( /__ ,__. __ __ / __ : / // / /__) / / /__) .+' Home: fre...@fcshome.stoneham.ma.us // (__ (___ (__(_ (___ / :__ 781-438-5471 Jude 1:24,25 - pgpVcvwr9FUMk.pgp Description: PGP signature -- fedora-list mailing list fedora-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
