Super Slow Performance with Xserve RAID / Promise Fibre

Question

Hey guys,
I am experiencing a strange thing on both 10.5.8 and 10.7.5 servers (yes these are in the process of being retired). They are sharing out either an Xserve RAID or Promise Vtrak with OS X Server.
We have the fibre channel card and the storage attaches to there and they appear mounted on the desktop.
The problem we are having is that whenever OS X's file sharing is enabled these volumes run incredibly slow! I did a clean install of OS X 10.7.5 on an entirely different machine and it was still bad. All of my tests show that when you turn off file sharing, both AFP and SMB, the performance goes back to normal -- so what can we do here??? These are file servers, so that's pretty much the only thing that needs to work.
Thanks,
Andrew

Answer 1

Slow/poor RAID performance can be down to a number of things. Some of which are easier to check than others.
Some easy things to check are:
How much data is stored on the RAIDs?
Performance really drops off alarmingly once the RAID gets to 85% full. For a 1TB RAID this means you need to keep at least 250GB of free disk space at all times otherwise you will get the poor performance you're seeing. Once it gets to 86/87/88% full performance can drop alarmingly. Yes those few percent points can make a big difference.
How is the data stored on the RAIDs?
Having thousands and thousands of single files stored loosely on the RAID or within one single folder is not a good idea. The Finder can be and is fairly inefficient at drawing the icons for those files that are presented to network users accessing the share point(s). This can/and is perceived as very slow performance as you're viewing the files over a network connection. One way to overcome this 'feature' is to organise the data into logical folders/sub-folders and/or shares.
Are there problems with the file/directory structure of the RAIDs themselves?
Use DiskUtility (or better still DiskWarrior) to repair any issues (generally built up over a period of time) with the storage disks you have. You can't repair permissions using DiskUtility or anything else on a non-OS bearing drive. Don't forget to do this also for your System Drive (which can have its permissions repaired) as well. This will mean the server being off-line for a time whilst the system (OS) drive is being repaired. Before doing this step I would make sure you have a current and effective backup of your System/Server OS as well as all data stored on the RAIDs themselves. Hopefully you should be doing this for your data already?
To understand Disk Utility's repair permissions feature please read Apple's support document here:
About Disk Utility's Repair Disk Permissions feature - Apple Support