Mehdi and David My experience is that control path failover is occasionally useful, the main instance being where a tape gets stuck in the control path drive, and the drive is unresponsive to its control path function while it repeatedly attempts to load the faulty tape. This happened repeatedly on an old 3584/LTO1 combination where the customer refused to replace the worn tapes, but continued to depend on them. However for a small to medium sized installation with new equipment I am not sure if the cost is worth the benefit. Reassigning the TSM library definition to another control path and restarting TSM can usually work around the problem.
For drives that can be dual attached this may be beneficial for load balancing, but again this should only be a concern for large installations or where an interruption to a lage data transfer will have serious implications, such as creating terabyte-sized individual backups or stgpool copies of these, and the time window is restricted. For LTO drives with one path or smaller installations, the extra expense of data path failover is usually not worth the benefit. TSM will normally pick up the error and restart the process anyway, on a different drive, and the errors that occur in practice are normally related to the tape rather than the drive or san. Even so, losing a single path to single drive does not normally cause TSM to fail though performance can be degraded. Total SAN switch failures are rare, and if they occur there may be data access problems that are more impacting than access to a tape drive. My only caveat would be that two drives are really not enough for a long term TSM installation, even a small one. A minimum of three are necessary to provide continued operation when the inevitable tape gets stuck in a drive. Regards Steve. Steven Harris TSM and AIX Admin Seeking AIX or TSM work, Sydney Australia David McClelland wrote:
Yes: for example, the IBMtape/Atape etc device driver can help your host to manage data path failover (DPF) for your drives and control path failover (CPF) for the library's robotics. It can also help with its dynamic load balancing feature as it tries to ensure that, if multiple paths exist from host to drive, the least utilised path gets used (depending upon OS/drive/driver you may need manually to configure this feature, and it may be at cost). Also consider that drives have different connectivity options - for example, IBM TS1120/1130 drives can be dual-attached to the SAN thereby potentially reducing the risk of isolation in event of a single SAN component failure, however LTO drives only have one fibre connection. /DMc -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Grigori Solonovitch Sent: 11 October 2009 12:09 To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] MPIO for tape libraries Of course, you need MPIO for fiber optics tape drives. It is not only high availability. It is better performance as well. Grigori G. Solonovitch Senior Technical Architect Information Technology Bank of Kuwait and Middle East http://www.bkme.com Phone: (+965) 2231-2274 Mobile: (+965) 99798073 E-Mail: g.solonovi...@bkme.com Please consider the environment before printing this Email -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Mehdi Salehi Sent: Sunday, October 11, 2009 1:57 PM To: ADSM-L@VM.MARIST.EDU Subject: [ADSM-L] MPIO for tape libraries Hi, Does it make sense to have MPIO for tapes? As tape libraries play an important role in TSM, their connection to hosts and specially to TSM server itself should be a reliable one. Should I expect to have link failover and/or load balancing for tape drives (something like SDDPCM, HDLM, ... for disk subsystems)? Thanks Please consider the environment before printing this Email. "This email message and any attachments transmitted with it may contain confidential and proprietary information, intended only for the named recipient(s). If you have received this message in error, or if you are not the named recipient(s), please delete this email after notifying the sender immediately. BKME cannot guarantee the integrity of this communication and accepts no liability for any damage caused by this email or its attachments due to viruses, any other defects, interception or unauthorized modification. The information, views, opinions and comments of this message are those of the individual and not necessarily endorsed by BKME." No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.420 / Virus Database: 270.14.3/2415 - Release Date: 10/08/09 06:39:00 ------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.421 / Virus Database: 270.14.10/2429 - Release Date: 10/11/09 18:34:00
