ADSM-L

Re: [ADSM-L] How does a library choose a drive?

2007-08-22 14:03:36
Subject: Re: [ADSM-L] How does a library choose a drive?
From: Paul Zarnowski <psz1 AT CORNELL DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 22 Aug 2007 14:00:18 -0400
Sorry to disagree, but I don't see how AIX can choose the drive - I
believe that TSM chooses it.  I don't know if it's LRU or
round-robin, but I do know that it attempts to spread the load evenly.

At 01:56 PM 8/22/2007, Mcnutt, Larry E. wrote:
Thanks Kelly, Richard and Andy for the quick responses.  So, as I
understand it in my scenario, it is the AIX host that chooses the drive
that is the "least recently used" one.  At the very beginning, it will
start at the first drive and sequentially go through them all and then
it will begin picking the "least recently used" drive to keep the usage
spread evenly across all the drives.

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Andy Huebner
Sent: Wednesday, August 22, 2007 12:26 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: How does a library choose a drive?

"Least Recently Used" I think is the management level explanation of how
it is done.

Andy Huebner

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Richard Sims
Sent: Wednesday, August 22, 2007 10:57 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] How does a library choose a drive?

On Aug 22, 2007, at 11:32 AM, Mcnutt, Larry E. wrote:

> TSM Server 5.3.3.0
> AIX 5.3
>
> This is probably not a TSM specific question, but hopefully someone
> can
> point me to the right place to look.
> We would like to understand how the library decides which available
> drive to use. ...

It doesn't decide: the host determines which drive to use.
TSM uses them rotationally, to balance wear.

For a 3494 library, see the MTIOCLM (Library Mount) library system
call in the IBM SCSI Device Drivers Programming Reference for the
nitty-gritty.  For a SCSI library, where the host has to engage in
more intricate control of library mechanics, I believe it's the
SMCIOC_MOVE_MEDIUM call (Transport a cartridge from one element to
another element).

    Richard Sims


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Manager, Storage Services                 Fx: 607-255-8521
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