It depends on how the RAID controller implemented RAID-10 (or RAID-1E). If your write request is small (and random as in TSM DB) you can easily hit read-before-write penalty usually found in RAID-5.
Zlatko Krastev IT Consultant Please respond to "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> Sent by: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] cc: Subject: Re: diskpool performance Hey, what the hell was your raid-10 like? Raid10 is by no means slower than raid1, if correctly implemented (by the means of the raid controller). I had it previously on an ICP-Vortex controller, and it was real blessing. But there are another curiosities as well - I see worse performance on IBM Raid Controllers using Raid-1E (raid 1 consisting of more than 2 disks) compared to Raid-1. More spindles, less performance, .. makes no sense as well.. regards Juraj Salak -----Original Message----- From: Roger Deschner [mailto:[EMAIL PROTECTED]] Sent: Wednesday, July 31, 2002 3:54 AM To: [EMAIL PROTECTED] Subject: Re: diskpool performance The disk storage pools need to be RAID-1+. It's "other people's data" and you are responsible for it, from the moment it is backed up from their client systems. As you have discovered, performance is not good with anything other than RAID-1. The Database and the Log also need to be RAID-1. (Mirrored by TSM or the OS or something) I tried striping (RAID-10, in effect) my TSM database, and caused a performance disaster that I had to back out of fast. The Log might survive RAID-5 without any performance penalty; I haven't tried it. Just remember that the Log is strictly write-only until disaster recovery becomes necessary. Roger Deschner University of Illinois at Chicago [EMAIL PROTECTED] On Sun, 28 Jul 2002, Seay, Paul wrote: >There is one caveat Mark. > >If the loss of a backup is a critical failure to an application, then you >must Raid-1 or Raid-5 the pool. I have applications that take processing >cycle backups several times throughout their processing cycle. I also have >servers that have to have the same backup cycle. So, an unprotected >diskpool is not a black or white answer to solving a performance problem. > >However, you are correct, RAID-5 is going to perform like crap for disk >pools unless you have ESS disk which have a very large disk cache on the >front and the RAID-5 turns into RAID-3 (no reads before writes because it is >always a full stripe write). > >Paul D. Seay, Jr. >Technical Specialist >Naptheon Inc. >757-688-8180 > > >-----Original Message----- >From: Mark Stapleton [mailto:[EMAIL PROTECTED]] >Sent: Sunday, July 28, 2002 1:46 AM >To: [EMAIL PROTECTED] >Subject: Re: diskpool performance > > >From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED]]On Behalf Of Dirk >Kastens >> Seemed to be a faulty raid controller. We always used raid5 for TSM >> volumes and never got any errors or bottlenecks. Of course, we use >> different raids for stgpools and the database. > >A question: why are RAIDing your TSM diskpool? There's no need for >redundancy in the diskpool, since the diskpool is not the mission-critical >component of your backup system. It's the *tape* pool you need redundancy >for, and that's what a copy pool is for. > >You *might* RAID 0 your diskpool, so that you stripe across the pool disks >for a larger number of read/write heads, but there's nothing but unnecessary >overhead when you RAID 5 it. The diskpool dies? You fix the pool, and you >back up the files again the next night. > >-- >Mark Stapleton ([EMAIL PROTECTED]) >Certified TSM consultant >Certified AIX system engineer >MCSE >
