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
