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 or other financial product or service, an official confirmation of any transaction, or an official statement of Merrill Lynch. Subject to applicable law, Merrill Lynch may monitor, review and retain e-communications (EC) traveling through its networks/systems. The laws of the country of each sender/recipient may impact the handling of EC, and EC may be archived, supervised and produced in countries other than the country in which you are located. This message cannot be guaranteed to be secure or error-free. References to "Merrill Lynch" are references to any company in the Merrill Lynch & Co., Inc. group of companies, which are wholly-owned by Bank of America Corporation. Securities and Insurance Products: * Are Not FDIC Insured * Are Not Bank Guaranteed * May Lose Value * Are Not a Bank Deposit * Are Not a Condition to Any Banking Service or Activity * Are Not Insured by Any Federal Government Agency. Attachments that are part of this E-communication may have additional important disclosures and disclaimers, which you should read. This message is subject to terms available at the following link: http://www.ml.com/e-communications_terms/. By messaging with Merrill Lynch you consent to the foregoing. -------------------------------------------------------------------------- ---------------------------------------------------------------------- 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
