Fiber devices

[Larry Basford]

We are converting our EMC 3830 from 24 scsi connections to 2 fiber switches and fiber connections. 5 to the EMC per sw. Can I expect to see an increase in disk I/O ? And I have never seen fiber devices what will I be seeing?

now
c6t1d0
c6t1d1
c6t1d2
c6t1d3
c6t1d4
c6t1d5

???

[Michael Tully · Accepted solution]

I would not expect to see any increase at all.
You will expect that the device numbering will definitely change. You'll need to export your volume groups and import them again. See this posting.

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=229622

[Steven E. Protter]

Configured correctly you should see an increase in performance.

A few factors to consider:
RAID level on the disk array, but if its the same array that doesn't matter.

Switch configuration.

Card chosen(there are 2 Gb and 1 GB models)

Our experience with a conversion to fiber showed a substantial performance increase.

We were replacing local scsi disk.

SEP

[Brian Watkins]

The device files for your disks will almost definitely change.

As previously mentioned, you will want to create mapfiles for all of your logical volumes so you can reimport them after the changeover. A full backup of the affected filesystems wouldn't hurt, either. You can never be too careful :)

From a performance perspective, you should see an increase in overall performance going to fiber.

One of the most important things to consider (next to your logical volume mappings/backups) is the SAN zoning. I'm assuming that EMC will be working with you on this conversion, so work closely with them to ensure that your SAN switch zonings are properly set up (check for proper path redundancy, no duplicate zones, each host only sees the EMC LUNs it needs to, etc.)

Good luck!

Brian

[doug mielke]

With 2 fiber switches I assume you'll use redundant pathing / failover.

If you get a chance, test the failover path, but even if you cant, definitly reboot the servers a couple of times to make sure the paths are configured, and stay configured correctly, and that the failover software does not try to alter anything.

[Larry Basford]

We were to get an upgrade to 16MB of cash in our EMC 3830. Found we don't have enough free slots. We can either drop from 5 fiber to the switch to 3 and add 2 4GB cards. add 1 4GB and get 12GB total with 4 fiber to each switch.

Your thoughts please.

Our application is very I/O intensive. And very rendom.

[Tom Hartsfield]

If you're IO intensive, you should look at a product from EMC called PowerPath. It does IO load balancing across multiple Fibre interfaces, and provides very smooth failover in the event that one of the paths fails (card, fiber, switch, whatever). It's not free, but if IO is a concern, it's worth it. Your EMC rep should be able to get you a quote.