Defragging RAID 5

[nunzeo]

Not sure if I am posting this in the right groups page but what are your thoughts on defragging a RAID 5 volume? I've read mixed reviews that say you don't need to defrag a RAID 5 because it works diffently, etc. But I believe that it should be defagged. I am speaking about hardware RAID. If we do not need to defrag RAID volumes than why would DiskKeeper or any other utility like that be needed.

Just trying to get more opinions.

Thanks, nunzeo

 

[Davetoo]

I've never defragged my RAID 5's in the seven years I've run our network.

I'm Certifiable, not cert-ified.
It just means my answers are from experience, not a book.

 

[nunzeo]

If you checked one of your severs where a large amount of storage is copied to and from everyday, don't you see a lot fragmentation in your defrag utility? Don't you experience any loss of performance? I just ask because I have a server that is completely RED on one of its data volumes. When we try to access data on that server we experience a lot of lag, but just pulling from that volume where there is a lot of fragmentation.

 

[itsp1965]

Regardless of RAID level you still get fragmentation on your drives. Although I don't do it often I have also defragmented my RAID volumes after a mass file deletion

 

[cpjust]

One of my servers looked just like that (totally red), and some files had over 100,000 fragments!
I tried to defrag it for a few weeks, but since some files are huge and there's not that much free space, I couldn't get rid of all the red...

 

[technome]

Defragging is up to you, but I defrag all client servers nightly if possible. If a server is moderately fragmented, (more like slightly), you get a 3-5% increase in speed on an Lsilogic based raid adapter, if it is defragged daily ( I have benchmarked this). If you do a boot time defrag, for programs which have open files such as SQL, every month or two, I would say those programs increase in speed at least 10%. Also if your arrays are highly fragmented, the disk heads need to move far more then necessary, which causes more current through the drive, thus more heat and wear. I do not like the option in third party defrag utils which are resident, and defrag on the "fly", as they cause a slight overhead during production hours


........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[nunzeo]

technome, you may think this is funny but i have 1TB of data on a 1.7TB storage volume that is completely red. do you recommend doing a check disk on this volume then a defrag? i know it would take me about a month of doing this during none business hours to get it fully clean.

do you have any other recommendations for me?

thanks for all your help and insight guys.

nunzeo

 

[technome]

I know large arrays are particularly difficult to allocate time for maintenance, but....

Definitely, if you have errors on the disk it can slow the array down, and the defrag program may refuse to work. Also, if your controller has a "consistency check" run it at least once a month, (checks the parity calcs).
More important, if it has the equal of "patrol reads", MANUALLY run this at least once a month. This checks ALL the sectors of the array...the raid adapter only checks the disk surfaces when accessing or writing data...errors buildup on unused space, sometimes more than an adapter can correct in a short period of time, thus causing multiple disks to fail at one time, the larger the array the more important this is.


........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[porkchopexpress]

@ nunzeo

Apparently MS don't use windows defrag for their sharepoint servers that hold massive amounts of data they use Perfectdisk as it's faster and can be run during periods of activity.