Redundant FC-AL connections for SAN tape library

[Doug Lucy]

We are laying out a new data center and one requirement is a high degree of redundancy. We have a rp8420 with multiple HBAs to a pair of SAN switches and a EVA 4400. That's all fine.

Our original configuration calls for a 2-drive FC-AL attached MSL4048 and DataProtector. However, after laying out the connection digram, it appears the MSL4048 has only one FC-AL interface and therefore can only attach to one, not both, of the SAN switches.

Is there a similar model in the MSL line that would have a second FC-AL port? Or something that would give us redundancy for the tape library's connection to the SAN?

Thanks in advance.

[TTr · Accepted solution]

Tape libraries/drives are not dual ported, at least I am not aware of any and neither of any software that could handle dual device files and path failover with tape drives like it is done with disks.

About the only thing you can do in your anvironment is setup an additional HBA with the FC cabling and the zoning in the second switch to change over the tape library manually if the first path fails. But I don't think it is worth doing, you will have a ton of work to do in your server to create the new tape device files and in your backup software to change all the tape device files to the new path.

To go even a step further, I would add a third SAN switch and use it only for tape traffic. This way the first two switches are dedicated for disk traffic and are perfectly balanced.

[Greybeard]

You don't say if the library is a fixed choice. There are libraries that allow direct Fibre to the drive cans and these can be zoned so a path failure would only take down half the capacity and jobs can be re-assigned. Or you could put in a backup server with 3 HBAs, one per switch and then to the lib thereby ensuring the sghortest possibble failure path and keeping the option of adding a disk array to the server for disk to disk to tape with dual path to the array next to the lib. this would allow load balanced throughput. Depends on budget really.