Yes I'm well aware of the different pro's and con's to using various levels of RAID vs non-RAID. In my application protection is paramount and mirroring is simply too wasteful to use. I've used RAID5 repeatedly in the past in regards to TSM and have always been very happy with the results. So the issue here isn't really what to use or not but rather whether there's any pro's or con's on the way you go about creating volumes on a RAID5 array. E.g. lots of smaller volumes or fewer large volumes? Having lots of RAID5 arrays as was also suggested isn't really practical because these days it's rare you don't have fairly large disks (18 or 36GB each) so in that example of 100GB you're really only talking 1 RAID5 array of 4-5 disks.
Bottom line is I was just speculating out loud perhaps on whether there were any pro's or con's to how many volumes and what size one would make the volumes on a RAID5 array. Say you had a 100GB RAID5 array. Would you create 10 10GB volumes or 2 50GB volumes? Does it matter since it's all just going into a big array? Regards, Gerald Wichmann Senior Systems Development Engineer Zantaz, Inc. 925.598.3099 (w) -----Original Message----- From: Gianluca Perilli [mailto:[EMAIL PROTECTED]] Sent: Tuesday, May 28, 2002 1:35 PM To: [EMAIL PROTECTED] Subject: Re: allocating disk volumes on RAID5 array Hi Gerald, I think you have to consider that if you use RAID5 logical drives, you have to calculate and write a parity every time you write any data on the disk: so if you have a write intensive application, RAID5 is not so efficient as other RAID protections (1,10, etc); if you have instead read-intensive applications RAID 5 is a good choice because it gives you the possibility to use more physical drives concurrently. Furthermore RAID 5 is the most efficient protection regarding the optimal usage of the available phisical capacity, and it is more and more efficient as the number of physical drives in the array increase; but at the same time as the number of physical drives increase, the performance goes down (because you have to calculate the parity on a larger number of blocks): probably the best compromise is a number of 7/8 disk drives/array. I hope this helps. Cordiali saluti / Best regards Gianluca Perilli Gianluca Perilli Tivoli Customer Support Via Sciangai n° 53 - 00144 Roma (Italy) Tel. 06/5966 - 4581 Cell. 335/7840985 Gerald Wichmann <gwichman@ZANTAZ. To: [EMAIL PROTECTED] COM> cc: Sent by: "ADSM: Subject: allocating disk volumes on RAID5 array Dist Stor Manager" <[EMAIL PROTECTED] .EDU> 28-05-02 21.14 Please respond to "ADSM: Dist Stor Manager" Since a RAID-5 array shows up as one big filesystem, what's the best strategy for determining how many and of what size disk pool volumes to create for your primary disk storage pool? For the most part I don't think it really matters unlike allocating volumes on individual disks but perhaps I'm not considering something. Thanks..
