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Defrag RAID 0?


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My PC is configured with 4 WD SATA II 120 GB 7200 RPM drives with RAID 0 (stripe) for enhanced drive performance. The Pitstop tests reports in repeated tests that the configuration is delivering 147 MB/sec performance, and ranks the setup in the top 1%.

 

The files are highly fragmented, and the Pitstop tests say that I should perform a defrag operation on the drives.

 

If I understand the RAID 0 (stripe) concept correctly, the fragmentation is desireable. Why would I defrag?

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Fragmentation is never desirable. The PC test and the OS see the drive as one big one.

Though the info is written over the four drives, it does not mean the are aligned contingently.

Installing and un installing will cause this. Defragging will align it to some extent, though

not perfectly.

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My PC is configured with 4 WD SATA II 120 GB 7200 RPM drives with RAID 0 (stripe) for enhanced drive performance. The Pitstop tests reports in repeated tests that the configuration is delivering 147 MB/sec performance, and ranks the setup in the top 1%.

 

The files are highly fragmented, and the Pitstop tests say that I should perform a defrag operation on the drives.

 

If I understand the RAID 0 (stripe) concept correctly, the fragmentation is desireable. Why would I defrag?

 

RAID 0 or a single physical drive is all the same as far as the Windows filesystem is concerned. NTFS sees the RAID 0 array as a single logical disk anyway, so it will suffer the same amount of logical fragmentation as a 'normal' single physical disk. The distinction between the physical components of the array is made by the RAID controller, not the file system.

Useful for understanding fragmentation and RAID:

http://downloads.diskeeper.com/pdf/new-sto...echnologies.pdf

http://files.diskeeper.com/pdf/FileFragmen...sNASandRAID.pdf

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  • 1 month later...

Trusting that all of the feedback telling me to defrag my highly fragmented 4 disk RAID 0 configuration would improve my performance, I purchased the PC Pitstop Disk MD software. Disk MD ran for a few hours, reducing the fragmentation to 0.1%. Another couple of additional passes, and the fragmentation has been reduced further to 0.05%.

 

Anxious to see the Disk Speed improvement, I logged on to PC Pitstop to run the Full Test again. No other changes have been made to my configuration. The Full Test returned a Disk Speed result of 142 MB/s, a reduction of 5 MB/s from my previous test.

 

Although there is normally a few points variability in the test results, previously ranging from 146 MB/s to 151 MB/s, a 142 MB/s result is a new low.

 

So... someone please tell me again why defragging a RAID 0 configuration is so important for disk performance. My evidence suggests otherwise.

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The OverDrive read/write test may be too short to get a good read, depending on how that specific array performs.

 

You may want to try a longer test. There is some pertinent information in this topic:

 

http://forums.pcpitstop.com/index.php?showtopic=164768

 

Even if OverDrive's disk test is not long enough to get into the the speedier read/writes, the defragmentation information is still correct.

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