Re: Help with zLinux DASD using multiple paths
On Mon, Feb 23, 2009 at 03:41:03PM -0500, David K. Kelly wrote: Thank you David and Ron for the quick responses. Let me explain what I'm trying to do. In zLinux I have a DB2 file system that is setup on one large 3390-27 disk pack. And when I use Linux tools like iostat I see one disk with one path to the Shark. What I would like to do is use the eight paths to this single disk (yes, I would like multiple exposures to the disks). How do I do that? Or maybe I already have this configured or CP is doing it but I can not tell this with my limited Linux commands? We do have Velocity and I can see lots of IO going through. Also we don't used PAV and from what I understand that is more of a zOS thing and we are a zVM shop. Let me explain it from the Linux point of view. For each disk linux sees it can submit one request at a time. Linux has no knowledge how this disk is connected to the storage system. So to submit more than one request at a time to the same disk there is only the possibility with PAV. If you can replace the one disk with set of smaller disks (rule: the more the better), this will boost the I/O. IBM published on http://www.ibm.com/developerworks/linux/linux390/perf/tuning_rec_dasd.html on how to set up storage configuration for good performance. The performance of a PAV with N paths and a striped volume with N disks is comparable. Ihno Thank you David K. David Boyes dbo...@sinenomin e.net To Sent by: Linux on LINUX-390@VM.MARIST.EDU 390 Port cc linux-...@vm.mar IST.EDU Subject Re: Help with zLinux DASD using multiple paths 02/23/2009 11:19 AM Please respond to Linux on 390 Port linux-...@vm.mar IST.EDU On 2/23/09 11:12 AM, David K. Kelly dkke...@courts.state.va.us wrote: How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I¹m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Just to be sure, do you want the Linux guest to see multiple exposures to the disk? If so, you need the PAV microcode to do that. If you just want it to exploit the physical paths, give the disk to CP as a user volume, allocate the disk as a minidisk in the Linux directory entry, and let CP worry about it. If the paths are in your IOCP, CP will automagically use them. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- Best regards/Mit freundlichen Grüßen Ihno Krumreich Never trust a computer you can lift. -- Ihno Krumreich i...@suse.de Projectmanager S/390 zSeries Maxfeldstr. 5 +49-911-74053-439 D-90409 Nürnberg http://www.suse.de SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg) -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Help with zLinux DASD using multiple paths
On Sat, Feb 28, 2009 at 2:34 PM, Ihno Krumreich i...@suse.de wrote: So to submit more than one request at a time to the same disk there is only the possibility with PAV. Would it not be the multi-path feature in Linux that allows Linux to see multiple exposures and an I/O outstanding to each exposure. PAV is what you need on LPAR to do this. With z/VM you can give the virtual machine multiple links to the same mini disk to simulate this. Whether that makes sense from a performance point of view depends on your configuration. With MDC in the picture, you can show cases where this works well. I have not been able to measure a configuration where z/VM uses PAV to back this. I have seen quite a few where it really made no sense at all. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Help with zLinux DASD using multiple paths
I need some DASD zLinux configuration help. How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I’m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Also has anyone used device-mapper-multiple? Thank you David Kelly The Supreme Court of Virginia
Re: Help with zLinux DASD using multiple paths
On 2/23/09 11:12 AM, David K. Kelly dkke...@courts.state.va.us wrote: How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I¹m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Just to be sure, do you want the Linux guest to see multiple exposures to the disk? If so, you need the PAV microcode to do that. If you just want it to exploit the physical paths, give the disk to CP as a user volume, allocate the disk as a minidisk in the Linux directory entry, and let CP worry about it. If the paths are in your IOCP, CP will automagically use them. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Help with zLinux DASD using multiple paths
David, I was just wondering what the objective of running multi path was. Is it to run PAV? Or is there some other reason? Is your mod 27 a full pack minidisk or is it going to have multiple minidisks? Ron Foster --Original Message-- From: David K. Kelly Sender: Linux on 390 Port To: LINUX-390@VM.MARIST.EDU ReplyTo: Linux on 390 Port Sent: Feb 23, 2009 10:12 AM Subject: Help with zLinux DASD using multiple paths I need some DASD zLinux configuration help. How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I’m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Also has anyone used device-mapper-multiple? Thank you David Kelly The Supreme Court of Virginia Sent via BlackBerry by ATT
Re: Help with zLinux DASD using multiple paths
Thank you David and Ron for the quick responses. Let me explain what I'm trying to do. In zLinux I have a DB2 file system that is setup on one large 3390-27 disk pack. And when I use Linux tools like iostat I see one disk with one path to the Shark. What I would like to do is use the eight paths to this single disk (yes, I would like multiple exposures to the disks). How do I do that? Or maybe I already have this configured or CP is doing it but I can not tell this with my limited Linux commands? We do have Velocity and I can see lots of IO going through. Also we don't used PAV and from what I understand that is more of a zOS thing and we are a zVM shop. Thank you David K. David Boyes dbo...@sinenomin e.net To Sent by: Linux on LINUX-390@VM.MARIST.EDU 390 Port cc linux-...@vm.mar IST.EDU Subject Re: Help with zLinux DASD using multiple paths 02/23/2009 11:19 AM Please respond to Linux on 390 Port linux-...@vm.mar IST.EDU On 2/23/09 11:12 AM, David K. Kelly dkke...@courts.state.va.us wrote: How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I¹m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Just to be sure, do you want the Linux guest to see multiple exposures to the disk? If so, you need the PAV microcode to do that. If you just want it to exploit the physical paths, give the disk to CP as a user volume, allocate the disk as a minidisk in the Linux directory entry, and let CP worry about it. If the paths are in your IOCP, CP will automagically use them. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Help with zLinux DASD using multiple paths
It's a characteristic of the architecture that all eight paths will be used under the covers, PROVIDING you can drive eight I/O operations at the same time to different volumes (or cache, for some subsystems, when reading). Normally you can't do this from a single guest. What you ARE getting is alternative to contention from OTHER guests going against the same storage subsystem. But if the database is on a single device, no matter how many paths you use, it will still only be one I/O at a time. Even with PAV and multipath, you won't get much help. On FCP, for example, we were advised not to use multibus mode (which load balances) due to overhead. The same issues probably apply to using PAV's with DASD (never mind the configuration issues). What you CAN do is use LVM to create a striped filesystem spread over eight smaller volumes (minidisks). We've run tests on this configuration and the performance was so much better, it's become our standard configuration for large data filesystems. -Original Message- From: Linux on 390 Port [mailto:linux-...@vm.marist.edu] On Behalf Of David K. Kelly Sent: Monday, February 23, 2009 3:41 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: [LINUX-390] Help with zLinux DASD using multiple paths Thank you David and Ron for the quick responses. Let me explain what I'm trying to do. In zLinux I have a DB2 file system that is setup on one large 3390-27 disk pack. And when I use Linux tools like iostat I see one disk with one path to the Shark. What I would like to do is use the eight paths to this single disk (yes, I would like multiple exposures to the disks). How do I do that? Or maybe I already have this configured or CP is doing it but I can not tell this with my limited Linux commands? We do have Velocity and I can see lots of IO going through. Also we don't used PAV and from what I understand that is more of a zOS thing and we are a zVM shop. Thank you David K. David Boyes dbo...@sinenomin e.net To Sent by: Linux on LINUX-390@VM.MARIST.EDU 390 Port cc linux-...@vm.mar IST.EDU Subject Re: Help with zLinux DASD using multiple paths 02/23/2009 11:19 AM Please respond to Linux on 390 Port linux-...@vm.mar IST.EDU On 2/23/09 11:12 AM, David K. Kelly dkke...@courts.state.va.us wrote: How can I configure multiple paths to a single disk in SUSE zLinux? I have 8 paths to our Shark and I¹m running zLinux SUSE 10 in zVM V5.3 on a z9 and I want to configure multiple paths to a single 22.8 GB 3390-27 disk. Just to be sure, do you want the Linux guest to see multiple exposures to the disk? If so, you need the PAV microcode to do that. If you just want it to exploit the physical paths, give the disk to CP as a user volume, allocate the disk as a minidisk in the Linux directory entry, and let CP worry about it. If the paths are in your IOCP, CP will automagically use them. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- This message w/attachments (message) may be privileged, confidential or proprietary, and if you are not an intended recipient, please notify the sender, do not use or share it and delete it. Unless specifically indicated, this message is not an offer to sell or a solicitation of any investment products
Re: Help with zLinux DASD using multiple paths
Actually, you *are* using all the paths the I/O subsystem in the hardware is already aware of them if they are defined in your IOCP. An I/O presented to the device by CP gets handed to the I/O processors. The I/O processors in the frame handle deciding which path to use at any given point based on what you told them in the IOCP gen. There can only be one outstanding I/O to a device number at a time, but that I/O can be (and is being) scheduled along whatever physical path is convenient and available at the time the command goes out and comes back. If you want to have more than one I/O outstanding at a time to the same device, you have to use PAV. It's the only architected way to do this. Z/OS is the biggest exploiter of PAV, but both Linux and VM know how to do it too. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
