ADSM-L

Re: [ADSM-L] Lousy performance on new 6.2.1.1 server with SAN/FILEDEVCLASS storage

2010-10-20 14:20:24
Subject: Re: [ADSM-L] Lousy performance on new 6.2.1.1 server with SAN/FILEDEVCLASS storage
From: Paul Zarnowski <psz1 AT CORNELL DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 20 Oct 2010 14:18:52 -0400
I/O to devclass file volumes will be inherently sequential, yes.  It's not an 
absolute, however.  There are varying degrees of "sequentialness".  Think about 
it this way.  When you are writing these volumes, they will definitely be 
purely sequential.  However, when reading them, they may or may not be purely 
sequential.  If you are only restoring say "active" backup files, then TSM 
would be skipping over the "inactive" files that can be interspersed between 
the active files.  Yes, they may have been "active" when they were written 
(depending on what did the writing - client or migration), but by the time you 
go to read the data, depending on what is doing the reading you may not be 
reading them purely sequentially.  Even if you are not reading them purely 
sequentially, I believe you will still likely reap benefits by having the 
blocks laid down on disk sequentially.  Note than when I say laid down on disk 
sequentially, this includes the idea of striping the blocks across spindles (if 
you are doing striping).  Striping does not defeat the sequentiality.

..Paul

At 02:11 PM 10/20/2010, Hart, Charles A wrote:
>Dumb statement, but isn't the whole Idea of the File Devclass is it is 
>sequential.  Can one be more sequential than the other?  If its not then its 
>random.
> 
>
>-----Original Message-----
>From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf 
>Of Paul Zarnowski
>Sent: Wednesday, October 20, 2010 1:07 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Re: [ADSM-L] Lousy performance on new 6.2.1.1 server with 
>SAN/FILEDEVCLASS storage
>
>How you connect to the disk storage (i.e., SCSI or SAN) doesn't matter.  This 
>goes more to the issue of how blocks within the volumes are laid out on the 
>spindles.  formatting them one at a time will cause the blocks to be laid out 
>in a more sequential fashion, so that when TSM references the blocks, they 
>will be referenced in a more sequential fashion (assuming you are doing mostly 
>sequential I/O).
>
>..Paul
>
>
>At 02:02 PM 10/20/2010, Zoltan Forray/AC/VCU wrote:
>>Thanks for the affirmation.  This is what I have been seeing/experiencing. 
>> As soon as I can empty the stgpool (5TB), I will define fixed volumes and 
>>see how much difference that makes.   I am aware of the issue of 
>>single-threading the define/formats to not fragment them, however I 
>>wonder how much that really matters in a SAN?
>>Zoltan Forray
>>TSM Software & Hardware Administrator
>>Virginia Commonwealth University
>>UCC/Office of Technology Services
>>zforray AT vcu DOT edu - 804-828-4807
>>Don't be a phishing victim - VCU and other reputable organizations will 
>>never use email to request that you reply with your password, social 
>>security number or confidential personal information. For more details 
>>visit http://infosecurity.vcu.edu/phishing.html
>>
>>
>>
>>From:
>>Markus Engelhard <markus.engelhard AT BUNDESBANK DOT DE>
>>To:
>>ADSM-L AT VM.MARIST DOT EDU
>>Date:
>>10/20/2010 09:20 AM
>>Subject:
>>[ADSM-L] Lousy performance on new 6.2.1.1 server with SAN/FILEDEVCLASS 
>>storage Sent by:
>>"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
>>
>>
>>
>>Hi Zoltan,
>>
>>my experience has been: use fixed size preformatted volumes, and be 
>>sure to format them sequentially, even if it seems to take a hell of a 
>>time. But then, it´s a one-time action and highly automated, so just 
>>don´t try to boost "performance" here. Make sure no one else is bogging 
>>perfs, SAN guys sometimes tend to put all kinds of unassorted loads on 
>>one storage array producing massive hot-spots during TSM activities.
>>
>>Kind regards,
>>
>>Markus
>>
>>
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>--
>Paul Zarnowski                            Ph: 607-255-4757
>Manager, Storage Services                 Fx: 607-255-8521
>719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu  
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--
Paul Zarnowski                            Ph: 607-255-4757
Manager, Storage Services                 Fx: 607-255-8521
719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu  

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