We decided to switch from single disk volumes to RAID 5 on our ADSM server.
Performance was one consideration but more important was our concern for
reliability for our HSM and 'archiving with delete' operations. We just
could not afford to loose a single disk volume with data before it made it
to tape. And we could not afford to go to mirroring... So RAID 5 it is --
for us.

Ken

> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
> Paul Fielding
> Sent: Wednesday, March 08, 2000 18:07
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: RAID vs. Separate Volumes
>
>
> I know this has been discussed before, but I'm interested in in current
> belief/discussions regarding this, out of context of someone's immediate
> problem.
>
> The whole question of whether or not to use RAID 5 for your
> database, logs,
> and disk pools.
>
> Here are my current understandings of the topic:
>
> - each volume defined to adsm gets it's own thread to work with, (db, log,
> or stg)
> - adsm does attempt to prioritize reads/writes within a thread to optimize
> them as much as is possible
>
> Assuming both of these to be true, the generic theory of life
> would be that
> one should be OK to do either of two things
>
> - have multiple disks, each with one volume on them (no raid), so
> that there
> are separate threads going to each spindle with no head contention.
> - have a single volume with a single thread, but make that thread really
> fast (lots of disk RAIDed together).
>
> This being said, I have had clients who have benefited from
> converting their
> raid sets (with multiple volumes on the set - read - head
> contention on all
> spindles) to individual volumes on sparate disks.
>
> I have also heard from others who claim they got better performance by
> switching to a raid set.  My thoughts here would be that if
> you're going to
> have a raid set, that you're better off making it one big massive
> volume so
> that you don't have head contention.  This of course comes at the cost of
> only having one thread.  Has anyone found a line where having multiple
> threads going to the single raid set would offset the head
> contention enough
> to make it worthwhile?
>
> What does everyone think about the different configs?
>
> Paul
>