Defrag RAID?

[Chrisroman]

Do you defragment your RAID array? How often, and what software do you use (Windows 7 x64) ?

On a side note... how often do you scrub your array?

 

[odditory]

Whether or not to defrag and/or scrub depends on the type of RAID array, what kind of data its holding, what kind of disks (spinning or SSD), etc.

In general, with the trend toward SSD's as O/S drive and large spinning disks for media storage/archival, defrag has become relatively inconsequential and legacy.

 

[Chrisroman]

Good point. I'm referring to a mechanical disk RAID. Data is 80% static. But I do use it as a scratch disk for CS5 editing.

 

[nitrobass24]

Depending on the OS Win Vista/08 and above the disk is already defragged in the background.

If you have XP/2003/*nix it wont hurt but depending on the frag% it might be a waste of time.

 

[Ron Caber]

Hey Chrisroman;

Diskeeper has been developing top-notch server level defrag software for a very long time so I thought I'd share a couple links that helped me decide how to set this up on our RAIDS:

RAID DEFRAG WHITE PAPER


Since SSDs are relatively new, the current popular belief is that they are more or less bulletproof and not susceptible to fragmentation like HDDs but in fact there is White paper indicating they are susceptible to their unique brand of performance deterioration so I thought you might find this link useful as well:

SSD DEFRAG WHITE PAPER

Hope this is helpful

Cheers!

 

[Cerulean]

If it's a SAN, don't do it. Just replace the HDDs with SSDs.

If it's a RAID, do it. It will improve performance tremendously if sequenced blocks are.. in sequence. Or just replace the drives with SSDs and you'll be good without defragmenting the RAID.

It literally took me about 1.5 to 2 weeks to defragment a 1.5TB RAID60 that had about 400GB used diskspace and contained PHDVirtual backups. The reason it is ok to defragment a non-SSD non-SAN RAID is because the first HDD will read its part, and then the second HDD has to find its part THEN read it, and the same applies to the rest of the HDDs that come after. Data is just randomly written on each disk wherever the head be at the time of receiving the write command, and because this is a RAID you lose more performance the more disks involved in the RAID than you would if you just had a heavily fragmented single physical drive.

You don't want to do it on a SAN because of the nature of SANs and VMware (assuming you are running that). At least at my workplace, defragmenting would be the worst thing we could possibly do because it would cause set storage areas to expand to full capacity, leaving little to no free space to use on the SANs for other projects and applications. For this, you're simply better off replacing the drives with SSDs. You'll get better performance and IOPs anyway.

Although Diskeeper is largely responsible for the new built-in defrag in Windows Vista and Windows 7, I would use either Diskeeper Pro Premiere (not free) or something like SmartDefrag (free). Reason being is that the built-in defragmenter is still basic and only runs on schedule at midnight or 2:30AM or something and is no proactive about preventing fragmentation on-the-go in the first place. At the very least, a program like SmartDefrag will automatically defragment every modified/new/moved file so that you practically don't have to defragment.