Defrag or not?

[Jeff Tolly]

Have DL380 G2's connected to a MSA1000 with all 14 drives occupied and an additional 14 occupied with 72Gig disks.

Been two years and have noticed some slow downs and after analyzing some of my logical drives from Windows 2000 Defrag util they are fragmented severely.

I've done a defrag on a server with RAID 5 with no problems but with a SAN I wanted to get your opinions on it.

Some of our logical drives are down to 3% - 10% available disk space. Have created other logical drives and moved files around to help the problem. Eventually we are going to reach our maximum capacity which is another topic.

Has anyone done this on a Compaq/HP SAN and can share their outcomes?

[Mark Poeschl_2]

I've used defrag utilities routinely on Compaq/HP HSG and EVA storage arrays, but my servers were Unix. The fact that you're on a SAN doesn't really affect whether defragging is a good idea or not.

And obviously defragging those really full drives is going to be a very time consuming and possibly fruitless undertaking.

[Sheldon Smith]

I agree. It is not going to matter if the disk free space is low.
As a guideline, consider that the defragger bundled with XP will complain if volume free space is less than 15%. You can *force* it to defrag the volume, but it will take excessive time to do it, since there is not a big area in which to put things. And, if there is much (any?) activity on the volume, the high end will always be "messy".

[Jeff Tolly]

I realize the 15% requirement and can move files to another partition or drive for that matter.

If I have 50% free space and the drive is 60% fragmented, should I go for it?

Without defragging over long periods of time the drives will get fragmented enough that you are not utilizing all that you can. Over time you are increasing the amount of space written to these disks. With the SAN maxed then you eventually run out of space. If you defrag, lets say quarterly, you can manage your disk space and increase performance.

So does performing a defrag on a SAN differ than doing it on a local RAID 5? Other threads have asked to consult with the Vendor and I did, they state "you can do it and have a complete backup if anything happens." So basically do at your own risk.

Thought I would see if anyone is doing this on a MSA1000?

[Felix Padovan]

Looking at the same issue on an MSA1000. Just wondering whether anyone has any recommendations on software products to use? Does HP provide a utility to perform SAN defrags?

[Uwe Zessin]

You won't get a 'SAN defrag'. A Fibre Channel based storage array simply talks serial SCSI protocol, a block-based data exchange - they absolutely have no idea what a file or even file fragmentation is.

[Felix Padovan]

So what product would you recommend to use, or are any products suitable ie. DiskKeeper etc. Or is it just not possible to defrag a SAN disk?

[Uwe Zessin]

Of course it is possible - if you look into the Windows registry, you will see that your 'SAN disk' will appear as a SCSI disk.