What type of drives are you emulating ?
How many drive are simultaneously used in full charge ?
What is the highest throughput you need ?

Anyway, you are obliged to define 16 drives by HBA...

>From my point of view, I will make the most simple choice :

HBA1 : drv1, drv5, drv9, and so on
HBA2 : drv2, drv6, drv10, ...
HBA3 : drv3, drv7, drv11, ...
HBA4 : drv4, drv8, drv12, ...

> -----Message d'origine-----
> De : ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] De 
> la part de Mcnutt, Larry E.
> Envoyé : jeudi 23 août 2007 16:05
> À : ADSM-L AT VM.MARIST DOT EDU
> Objet : Re: [ADSM-L] How does a library choose a drive?
> 
> Hi Pierre, et al.
> 
> We are in the process of adding a new VTL to our TSM server, 
> and we are trying to understand if there is a way to 
> configure the drives that will spread the I/O load across the 
> available fcsi ports.  The AIX server has 4 4GB fibre 
> connections to the VTL appliance.  We are emulating a Quantum 
> P3000 library with 64 drives.  When we initially configure 
> the library with all 64 drives, they are divided across the 4 
> fibre ports with port 1 having drive1-drive16,
> port2 drive17-drive32,
> port3 drive33-drive48,
> port4 drive49-drive64.  
> 
> We thought this may not be an optimal setup if TSM uses a 
> round-robin algorithm.  So, we recreated the configuration.  
> This time we defined 16 drives initially, which were then 
> spread across the 4 fibre ports with port1 drive1-drive4,
> port2 drive5-drive8,
> port3 drive9-drive12,
> port4 drive13-drive16.  
> 
> Then we went through the process 3 more times until we had 64 
> drives defined.  This results in the having the drives 
> defined across the 4 ports as: 
> port1 drive1-drive4, drive17-drive20, drive33-drive36, drive49-drive52
> port2 drive5-drive8, drive21-drive24, drive37-drive40, drive53-drive56
> port3 drive9-drive12, drive25-drive28, drive41-drive44, 
> drive57-drive60
> port4 drive13-drive16, drive29-drive32, drive45-drive48, 
> drive61-drive64
> 
> This seems like a better configuration for a round-robin 
> drive assignment.  It was at this point that we thought we 
> should try to learn how the drives are assigned.
> 
> Thanks for any suggestions or pointers.
> 
> Larry
> 
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] 
> On Behalf Of CAYE PIERRE
> Sent: Thursday, August 23, 2007 5:36 AM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: How does a library choose a drive?
> 
> Hi,
> 
> From my observations, it depend of the action TSM is doing.
> 
> For example, when TSM is in initialisation state, there is a 
> validation of all the drives, in element addresses order.
> When TSM is doing an audit libr checkl=y, it work the same 
> For that cases, and others, concerning ALL drives, TSM seems 
> to act in element adresses order
> 
> BUT when doing recurent task, as backup and so, TSM SEEMS to 
> act as Richard explain, asking the OS for a drive, so it's 
> the OS which make the choice, based on it own algorythm.
> 
> Larry, what are the reason why you want to know that point ?
> 
> Pierre
> 
> > -----Message d'origine-----
> > De : ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] 
> De la part 
> > de Kelly Lipp Envoyé : mercredi 22 août 2007 20:56 À : 
> > ADSM-L AT VM.MARIST DOT EDU Objet : Re: [ADSM-L] How does a 
> library choose a 
> > drive?
> > 
> > I'm with Paul: TSM chooses the drive and based on my observations 
> > always does round robin.  Not LRU as I don't think it keeps 
> track of 
> > that.  So it will choose the next drive in order as long at 
> that drive 
> > isn't in use.  If in use, skip to the next and keep going around.
> > 
> > You see this on label libvol commands in particular. 
> > 
> > 
> > Kelly J. Lipp
> > VP Manufacturing & CTO
> > STORServer, Inc.
> > 485-B Elkton Drive
> > Colorado Springs, CO 80907
> > 719-266-8777
> > lipp AT storserver DOT com
> > 
> > -----Original Message-----
> > From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] 
> On Behalf 
> > Of Paul Zarnowski
> > Sent: Wednesday, August 22, 2007 12:00 PM
> > To: ADSM-L AT VM.MARIST DOT EDU
> > Subject: Re: [ADSM-L] How does a library choose a drive?
> > 
> > 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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> > 
> > --
> > 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
> > 
>