Mehdi, >>> Does defining logical tape drives helps eliminating this single point of failure such that if during client backup the fiber connection of drive fails, another tape drive in the library takes over the operation?
Okay, the quote from the Redbook below may have misled you in this case: a 'logical tape library' as you describe below is quite different to the concept you describe as a logical tape drive, it is how IBM describe their library partitioning. Here, creating 'logical libraries' (i.e. a library partition) will allow you to share a single physical library amongst, for example, Netbackup, Mainframe and TSM applications and the partitioning is managed by the library itself (e.g. with ALMS in a TS3500/3584) and has nothing to do with any virtualisation/logical definitions within TSM or the OS. The tape drives themselves here are not virtualised: you're still accessing a *physical* tape drive device, and a failure of a physical LTO drive, or the path to it, will still result in that path/drive going offline - potentially interrupting a data movement operation, although as Steven has also pointed out, TSM's normally pretty hot on these and may retry the operation on a different drive. Hope that helps, /DMc London, UK -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Mehdi Salehi Sent: 12 October 2009 06:42 To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] MPIO for tape libraries For logical tape libraries, please look at this excerpt from SG24-5946-06: " Multiple logical libraries are an effective way for the library to simultaneously back up and restore data from heterogeneous applications. For example, the library can be partitioned so that it processes: - Commands from Application 1 (about Department X) in Logical Library A - Commands from Application 2 (about Department Y) in Logical Library B - Commands from Application 3 (about Department Z) in Logical Library C In this configuration, the storage slots and drives in each logical library are dedicated to that library and are not shared among other libraries. Commands issued by the applications travel to the library through three unique control paths. Thus, the data processing for: - Department X is confined to the storage slots and drives in Logical Library A - Department Y is confined to the storage slots and drives in Logical Library B - Department Z is confined to the storage slots and drives in Logical Library C" No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.421 / Virus Database: 270.14.3/2415 - Release Date: 10/11/09 06:39:00 -----Original Message----- From: David McClelland [mailto:t...@networkc.co.uk] Sent: 11 October 2009 18:18 To: 'ADSM: Dist Stor Manager' Subject: RE: [ADSM-L] MPIO for tape libraries I'm not quite sure I know what you mean by 'defining logical tape drives', without a VTL or somesuch. Can you expand technically upon what you mean? >From my experience, the majority of failures involving tape drives have been down to drive/head mechanics failure or tape cartridge errors (although I note that this seems to be increasingly uncommon these days), rather than physical fiber component failure. In these instances, any amount of multi-pathing can't help and you need to make sure that you have enough spare capacity in your library/design to cope, and an alerting/support process in place which can recognise it and get it resolved as quickly as possible. Given that most of your backup clients will (presumably) initially write to TSM-managed disk storage pools (except SAN Storage Agents and perhaps NDMPs etc) hopefully a drive failure won't have a direct impact upon a client backup data integrity, as TSM tends to be pretty precious about this when performing migrations/data movement operations involving tapes. /DMc -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Mehdi Salehi Sent: 11 October 2009 17:13 To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] MPIO for tape libraries Thanks David, you made a good point about single fiber connections of LTO drives. Does defining logical tape drives helps eliminating this single point of failure such that if during client backup the fiber connection of drive fails, another tape drive in the library takes over the operation?
