IBM xSeries 346: slow RAID configuration

[deflagg]

We have an IBM xSeries 346 server (2x3.6 Xeon processors, 2GB RAM) with a RAID 5 configuration and Windows 2003 Server installed. When we copy a 0.5GB file from the local drive to the drive array, the time to do this is extremly slow. The results aren't even consistent, and it gets slower each time we do it. Then we tried to copy a 0.5GB file from the drive array to the local drive. On the first try, it was copied in 3 seconds. Every subsequent time we copied this file (from drive array to local disk) we couldn't obtain 3 seconds. Actually, we were getting times like 2 - 4 mins, each time getting slower and slower. We thought maybe it was because of the RAID 5 configuration, but we still should be getting consistent results. Before I get any replies, I must tell you I'm not a computer engineer. My expertise is in software engineering, so please explain whats going on in simple terms .

 

[technome]

First find out if it is the raid or the network.

For a raid, test copy a directory with say 800 meg of mixed data files from one directory to another, time it.

On my AMD dual Opteron server, with a PCI-X raid, 800 Meg copied from one directory to another directory, on the same array set (same volume) taking..
Raid 1 35 seconds
Raid 5 38 seconds

If you do not get decent throughput make sure write back is enable in the raid card setup parameters. Read-ahead is another parameter which helps if you have an option to enable it in the setup.

Time the same copy over the network to a workstation
On a single cpu dell 2800 3.2 Ghz, with a perc4E raid, 700 meg takes 80 sec to copy 700 Meg to a 3.0Ghz workstation.

Play with the flow control on the server network NIC (advanced properties of the network card), on/off. Flow control is some times needed but is is not need on 3 devices..wks, switches, server; it is only needed on one of them, if at all; on switches is probably the best bet, if you have managed switches, as non managed switches do not have an interface to change switch parameters.

Your network security permitting, turn off SMB signing. Search google for Windows SMB disable

Lastly you may have cabling errors which are slowing the network down. This would require testing the cables with a tester capable of cat 5 or 6 certification. Telco installers, or network consultants have these.

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