Hi First off, the number of spindles is not the only important factor. What kind of disk are you using for the database? Do you have a disk cache for read / write caching or is it JBOD in a machine?
Second off, to aquire maximum performance on a limited amount of spindles, I suggest you use the mirroring feature within TSM and use parallellism. That way, TSM will have the ability to read / write from multiple DB copies containing the same information. It will also protect you from a partial write, something that hardware mirroring / striping wont. Remember to use TSM's shadowing in thise case or the partial write protection is gonna be lost if you use parallellism. To say what is the best setup for your particular environment isnt that easy since we're missing out factors such as size of database, amount of memory available for DB cache (bufferpool). How you treat the log will also be an impacting factor in your setup. In the case of DB, RAID-5 isnt always a bad choice. DB writes/read are quite random. And the % of reads compared to the % of writes will also affect any performance gain you will get from using striping (RAID-0) since striping will give you a performance gain from writes, but in the case of a TSM DB not when it comes to reads. In my opinion, 4 physical disks are abit low if it comes to holding both primary and secondary copies of the database and still have enough DB volumes. According to TSM performance redbooks, 6-8 DB volumes (in some cases I have seen number saying 8-12, but that obviously depends on the size of your database) is a good setup for gaining a good performance, but with only 4 spindles, you're limited to only 4 (placing more than 1 copy on each spindle is gonna reduce performance if this is JBOD disks). Therefore, depending on the size of your database, I would say going with 2 main DB copies and 2 secondary DB copies would be a good choice. If the disksubsystem you're using doesnt have write/read cache, you might consider placing the volumes on a JFS-2 filesystem instead of using raw devices (which I usually use when I have a disksubsystem with a large amount of memory cache) to gain advantage of AIX's file system cache. You will however in this case have to adjust the MINPERM and MAXPERM settings (you adjust these settings with the vmo command) for how much memory the system is allowed to use for filecaching to adjust your system to work optimal. Remeber not to kick up both your DB bufferpool and the filesystem cache since if these both start fighting for memory, you'll end up getting your bufferpool data or filesystem cached paged instead, which will reduce performance. Best Regards Daniel Sparrman ________________________________________ Från: ADSM: Dist Stor Manager [[email protected]] för Oscar Kolsteren [[email protected]] Skickat: den 19 februari 2009 09:04 Till: [email protected] Ämne: Re: 4 spindles for db: best performing setup Hi Michael, I have a similar environment and created two RAID 0 lun's of 2 disks each. The mirroring is done in TSM itself. I'm more interested in what segment size people use on the disks and if a certain pp size is recommended for a volume group under AIX. Good luck Best Regards, Oscar -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[email protected]] On Behalf Of Michael Green Sent: 18 February 2009 20:23 To: [email protected] Subject: [ADSM-L] 4 spindles for db: best performing setup You are given 4 spindles to place TSM DB on them. How would you set them up to squeeze maximum performance for DB? 1. Dedicate each spindle for a DBC (result: 3 DBCs, one spindle left out, nevermind) 2. Create RAID 0 out of each pair of disks. Place a DBC on each RAID (result: 2 DBCs on two separate RAID 0) 3. Create RAID 1 out of each pair of disks. Place a DBC on each RAID (result: 2 DBCs on two separate RAID 1) 4. Create RAID 5 out of all spindles. Place one DBC on the RAID (result: 1 DBC on RAID5) Notes: a. There is no RAID 0+1 c. Wasted space is not a concern -- Warm regards, Michael Green ************************************************************************ ******************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by an antivirus scanner for the presence of computer viruses. ING Direct NV is a limited liability company incorporated in The Netherlands. 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