ADSM-L

Re: TSM Database Disk Layout Recommendations

2002-10-07 18:25:01
Subject: Re: TSM Database Disk Layout Recommendations
From: Bernard Rosenbloom <brosenbl AT OPTONLINE DOT NET>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Mon, 7 Oct 2002 18:25:46 -0400
I agree that RAID-5 is not good for TSM( DB,LOG or Stg pool voulmes). Basic
reason is poor performance. But I can't find any literature to back the
statement up. I'm having trouble convincing the IT architects....need hard
facts..any ideas?

Zlatko Krastev/ACIT wrote:

> 2. There definitely is a reason NOT to use RAID-5 for TSM. If you want
> your TSM server to snake like a worm put DB and Log on RAID-5, especially
> with a big stripe size - one of the best methods to shoot yourself in the
> leg. RAID-5 for diskpool volumes also will have performance impact but not
> so disastrous. It seems like you have enough disks to use mirroring or
> RAID-1 so why not.
> I still prefer to use raw LVs instead of filesystems despite the fact
> community on this list cannot completely agree is there any significant
> benefit or penalty for doing so. Using 'mklv -t tsm_db', '-t tsm_log' and
> '-t tsm_vol' fairly well describes what those LVs are for and I am not
> forced to exclude the files for the client on the server itself. IMO raw
> LVs are few percent faster than JFS files, there is no need to worry about
> large-enabled filesystems and file I/O buffering does not consume the
> memory TSM server can use better.
>
> 1. 8x 9GB after mirroring will give you 36 GB. It looks to be enough for
> both DB and Log. If your DB is not under 27 GB (cannot fit in three disks,
> you wrote <30) and you cannot afford 9-th and 10-th disk (DB and Log on
> separate disks gives best performance) you will be forced to use same
> disks for DB+Log. Create 1-1.5 GB LV in the center of each disk for Log.
> Create one or two LVs on the same disks for DB. It is recommended to
> mirror them through TSM but you can also use AIX mirroring or RAID-1.
>
> 3. For both DB and diskpool volumes it is better to have one (IMO) volume
> per disk. Other people on this list suggest more than one but opinions are
> consolidated that more than few will have negative impact on performance.
> Disk head moves will prevale disk reads/writes and performance will
> suffer.
>
> Zlatko Krastev
> IT Consultant
>
> "Varney, Patrick" <PAV5 AT PGE DOT COM>
> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
> 30.09.2002 22:21
> Please respond to "ADSM: Dist Stor Manager"
>
>         To:     ADSM-L AT VM.MARIST DOT EDU
>         cc:
>         Subject:        TSM Database Disk Layout Recommendations
>
> Hello All,
>
> I'm sure that this general question has been asked many times, but every
> situation is different. And I can't seem to get to the www.adsm.org site,
> so
> here goes.
>
> We just received some new SSA disks for our TSM servers and I'm looking
> for
> some advice on the best way to lay everything out. Here are the details on
> our planned environment (the SSA configuration has not been done yet, so
> it's flexible):
>
> Server:
>   RS/6000 7026-H70
>   4-way processor
>   4GB memory
>   1 SSA HBA (2 loops)
>   AIX 4.3.3 ML 10
>   TSM 4.2.2.12
> Internal SCSI Storage:
>   4 x 9GB (current TSM database/log location)
> SSA Loop 1:
>   8 x 9GB
>   RAID 5
>   Approx. 60GB
> SSA Loop 2:
>   8 x 72GB
>   RAID 5
>   Approx. 500GB
> TSM Database:  Less than 30GB
> TSM Log: 3-4GB
> Disk Storage Pools: 300GB
>
> My current plan is to put the TSM database on the 9GB SSA drives (using
> RAID
> 5, no TSM mirroring), the disk storage pool volumes on the 72GB SSA
> drives,
> and use the internal 9GB drives for database dumps to disk. However, I'm
> open to suggestion. Specifically, I am looking for answers to the
> following:
>
> - Where is the best place for the TSM database log volumes? And if they
> are
> sharing space on the SSA disks, is there any advantage to creating a
> separate file system (in general, is there any performance
> advantage/disadvantage to multiple file systems on one SSA RAID array)?
> - Is there any reason to NOT do RAID 5 on the SSA disks?
> - For the database and disk storage volumes, is it better to create more
> smaller (2GB) volumes or enable "large file" support and create fewer?
>
> Any help would be greatly appreciated.
>
> Thanks,
>
> Patrick Varney
> Pacific Gas & Electric Company
> Fairfield Information Operations Center (FFIOC)
> Enterprise Services  Group (ESG), Senior Network Specialist
>         *  internal 8-227-2823
>         *  external 707-436-2823
>         *  pager 707-288-1513