It seems the perfect environment for the JBOD I suggested as you do not want 
all those sessions banging a RAID5 array.

Of course work flow is an issue, but the moving a TB disk to disk or disk to 
tape is a couple of hour process if you work it correctly into your daily 
processing and probably isn't an issue for you.  Ideally you wouldn't need to 
move it again, but you really can't have that many sessions banging RAID5 so 
what else do you do?

I've arrived at this approach pragmatically and through trial and error.  I 
know that I can easily run fifty or sixty (and perhaps more) sessions to 12 SAS 
15K drives (use two disk pool volumes per drive to saturate each drive).

Kelly Lipp
CTO
STORServer, Inc.
485-B Elkton Drive
Colorado Springs, CO 80907
719-266-8777 x7105
www.storserver.com


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Michael Green
Sent: Thursday, August 06, 2009 4:04 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] I'm getting new disk storage.

On Tue, Aug 4, 2009 at 7:41 PM, Kelly Lipp<lipp AT storserver DOT com> wrote:
> You are exactly correct: modeling what will be rather than what is can be 
> tricky.  The problem really boils down to not having enough data to really 
> play with it adequately.
>
> I can tell you from experience on probably 200 TSM servers (Windows 2003 
> based, which is just fine all of you AIX heads!) that your overall scheme is 
> good.  One additional, I like to run initial backups to SAS drives using a 
> storage pool of device class disk.  Don't protect those drives simply use 
> JBOD as you will migrate the data out of them fairly soon either to tape or 
> file device class disk.  Use RAID5/6 for your SATA drives (We generally use 6 
> drive RAID5 sets in 12 bay shelves and 8 drive in 16 bay shelves) and keep a 
> smallish number of simultaneous backups to pools there as large numbers of 
> backups thrash the RAID set something awful.
>

Your suggestion of using JBOD instead of RAID for DISKCLASS data is
intriguing... I accept the reasoning behind not protecting these
drives by RAID. But how does it affect the workflow performance-wise?
What is the rational behind this? Economy (no wasted drives for
parity), performance gains?


>
> How much data do you backup today?  How many clients simultaneously? If you 
> want to take this private, give me a call.  I have a pretty good idea how to 
> size this if I have some more information.  Perhaps can save you a testing 
> step (testing costs money that you could spend on additional storage...).

That particular server backs up  700-1000GB  (~400K+ affected objects)
coming from just under 100 nodes nightly.
Thanks for offering me a phone consultation :) I won't bother you for
the time being, but maybe I will at a later time :)

>
> Thanks,
>
> Kelly Lipp
> CTO
> STORServer, Inc.