Hello guys,
I've a bit of puzzle with a client's storage system... The setup is quite simple: physical windows 2003 servers with SnapDrive atatched LUNs over iSCSI on FAS2020.
Issue: all the LUNs they've set up for their Windows Server platforms suffered a sudden drop of performance. Subsequent analysis of the system we carried out showed only fragementation issues as the probably culprit - up to 12 on one of the LUNs. All else seemed to be working fine, network tested, LUNs properly alligned, all services up & runing.
After several reallocation jobs across all volumes/LUNs, the fragmentation levels are now below 1,9. In some cases, it brought about more-less better performance but on one particular LUN the READ performance is attrociously poor. Most of the time it's under 1-2MB/s, even when there's hardly any work load on the storage side! 😞
The problem is that this LUN is extremely important for them. Moreover, it was the only reason for setting up a storage system - to raise it's data availability. We've opened up a case with NetApp support and sent them perfstat reports they've requested but, by the looks of this, it will require a lot of time to resolve the problem.
Now... Since the LUN in question is only 150 gigabytes in size, our first reflex was to move the data to a local disk on the server untill we figure out what's wrong with iSCSI. But the read performance is so poor it would take us at least 8-10 hours to complete the migration. There are a few snapshots we also tried using for copying but since they're point-in-time images of that same, slow LUN, performance was equally disappointing.
So I've mapped up a new LUN to the same server and tested it's performance. Suprisingly, it was OK. So now I'm thinking - if we could somehow migrate the data to a new LUN, internally, perhaps we can avoid the slow read problem. Any ideas on how to do that? Do you suppose that would help?
Thanks,
Igor