# Do you defrag your Raid setup?



## Chim3ra

It's a good question. My answer may not be definitive but it will hopefully get some wheels spinning.

In RAID 0 since data is already split up due to striping, it could be more problematic than helpful. What I'm saying is when the HDD is defragged, it's essentially moving data. Now, if the data is split up, when the HDD tries to move it will it be moved to only one disk? Will it remain in a striped configuration? That's what really gets me.


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## muffin

You see 2 blocks of data? I see:


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## Mastacator

Tell you what, since I am still in the process of deciding how I want my raid setup, I will test it both ways. Run some benchmarks on it right after setup, then run the same after a defrag. See if it makes some kind of difference.


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## pauldovi

Quote:


Originally Posted by *muffin*
You see 2 blocks of data? I see:










Lol! I think you need to defrag....


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## Lando95

Quote:


Originally Posted by *Mastacator*
Tell you what, since I am still in the process of deciding how I want my raid setup, I will test it both ways. Run some benchmarks on it right after setup, then run the same after a defrag. See if it makes some kind of difference.

Hey Mast, would you mind taking a screenshot of the "analyzed drive" just like you did above, both right after your install, and then again right after a defrag?

And yes, I have files on the left side, then a gap, then files on the right. I don't have 3 seperate areas like you do.

Quote:


Originally Posted by *Chim3ra*
Now, if the data is split up, when the HDD tries to move it will it be moved to only one disk? Will it remain in a striped configuration? That's what really gets me.

That is what I am wondering also. No clue


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## pauldovi

Contract WD tech support and see what they have to say...


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## sccr64472

Quote:


Originally Posted by *Lando95*
This is something I have been wondering about for a couple years now, but I haven't been able to find any solid evidence either way. Should you or should you not defrag a Raid 0 setup?

When you analyze your disks using Windows XP, I noticed that the data seems to be split into 2 pairs. I presume this is the 2 hard drives, but I don't know for sure if the picture is a true graphical representation of data on the drives.

Since the raid controller already splits up the data, is Windows going to see these data clusters as fragments? Or, will Windows put the files in their proper place utilizing raid?

Anyone have a definitive answer?

Windows doesn't know that it's 2 physical drives. All Windows sees is a location where the data is held. If it's not sequential, Windows will see it as fragmented. When loading data onto a striped array, these locations are alternated between the 2 physical disc drives, but Windows won't know that and doesn't care. Defragment it








Edit: To comment further, this is somewhat similar to sticks of ram with ICs on them. Windows doesn't care which physical stick the data is on or whether it's single sided,double sided, etc....all it needs to know is the address of the data. It's the same thing with your hard drive, whether a single drive or a striped array.


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## Mastacator

Quote:


Originally Posted by *Lando95*
Hey Mast, would you mind taking a screenshot of the "analyzed drive" just like you did above, both right after your install, and then again right after a defrag?.....

Yeah, I will. See if it is much different.

Quote:


Originally Posted by *sccr64472*
Windows doesn't know that it's 2 physical drives. All Windows sees is a location where the data is held. If it's not sequential, Windows will see it as fragmented. When loading data onto a striped array, these locations are alternated between the 2 physical disc drives, but Windows won't know that and doesn't care. Defragment it









If windows won't know and doesn't care, then wouldn't it put the files back together when defragmenting, instead of striped across? Still seen as one disk just not striped, so it would be like JBOD instead of raid 0.


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## sccr64472

Quote:


Originally Posted by *Mastacator*
If windows won't know and doesn't care, then wouldn't it put the files back together when defragmenting, instead of striped across? Still seen as one disk just not striped, so it would be like JBOD instead of raid 0.

No, because when the array is created, Windows thinks that the sequential addresses are alternating between the drives. Do you see what I'm saying? If address location 0000 is on the first drive, 0001 is on the second,etc.


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## Lando95

Quote:


Originally Posted by *Mastacator*
If windows won't know and doesn't care, then wouldn't it put the files back together when defragmenting, instead of striped across? Still seen as one disk just not striped, so it would be like JBOD instead of raid 0.

I think what he is saying is that Windows only detects 1 logical drive, and the raid controller does the rest.

Quote:


Originally Posted by *pauldovi*
Contract WD tech support and see what they have to say...









Come on now, that would be _way_ too easy


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## Mastacator

Quote:



Originally Posted by *sccr64472*

No, because when the array is created, Windows thinks that the sequential addresses are alternating between the drives. Do you see what I'm saying? If address location 0000 is on the first drive, 0001 is on the second,etc.


So it will defragment the smaller files on each drive that make up the big file broken up by the controller for the raid, and just put them in the right sequence, but not reassembly the file as though it were on a non striped disk array?


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## Mastacator

Quote:



Originally Posted by *Lando95*

I think what he is saying is that Windows only detects 1 logical drive, and the raid controller does the rest.


Thats more of what I was thinking, windows sees it as one drive, but the controller reads/writes the data, so it does its job and splits up the file per drive. So defragmenting the controller reads the file "parts", assembles them to a single file, then breaks it back up to be written appropriatly to the raid.


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## sccr64472

Quote:



Originally Posted by *Mastacator*

So it will defragment the smaller files on each drive that make up the big file broken up by the controller for the raid, and just put them in the right sequence, but not reassembly the file as though it were on a non striped disk array?


Windows only needs to be able to read/write data, period. It could careless whether that data is on a sata drive, an IDE drive, an optical drive, a striped array, ram,etc. On a striped array, the addresses are split to be physically alternating between the 2 drives (or more in a matrix) and is controlled by the Raid controller. Windows has no idea where the data is coming from and doesn't care. Look at pagefile, windows doesn't care if it's your hard drive or ram that holds the data, it just asks for data to be retrieved and for data to be written. If you defragmented your hard drive, it will attempt to defragment it the exact same way it attempted to write it initially...by sequential addressing.


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## ICYUNVME

I defrag my raid array all the time with no ill effects at all. I wish I still had the sites I was researching raid on but the sites basically said that defragging a stripped array is very necessary due to the set cluster size causing some files to be fragged to maintain cluster size. Im at work right now but tonight when i get off ill look for the link to post it to read.


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## busa

Quote:



Originally Posted by *sccr64472*

Windows only needs to be able to read/write data, period. It could careless whether that data is on a sata drive, an IDE drive, an optical drive, a striped array, ram,etc. On a striped array, the addresses are split to be physically alternating between the 2 drives (or more in a matrix) and is controlled by the Raid controller. Windows has no idea where the data is coming from and doesn't care. Look at pagefile, windows doesn't care if it's your hard drive or ram that holds the data, it just asks for data to be retrieved and for data to be written. If you defragmented your hard drive, it will attempt to defragment it the exact same way it attempted to write it initially...by sequential addressing.


DING<DING<DING....we have a winner. Windows just sends the files back and forth. The raid controller tells the data where to go. I defrag my HDD's all the time just like there was no raid.


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## Lando95

Good deal guys, thanks for the info!!


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## Strider_2001

I am suprized that there is not sofware ot already that supports the defraging to both hard drives to make it more profitable...


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## Burn

Quote:



Originally Posted by *Strider_2001*

I am suprized that there is not sofware ot already that supports the defraging to both hard drives to make it more profitable...


 RE that, no software-based program can do that because it will always read it as 1 physical drive no matter what you do...

@ Lando, I ran some ATTO and speed tests that saw my top seek and random read speeds when I first installed and formatted the array, several months later I re-ran them and saw a drop in performance, not that much, but a little bit off the top. I don't know if this could be due to more programs installed or not, perhaps due to defragging.


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## markuk3

Defrag on a weekly basis with raid 0 never had a problem for two years


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## sccr64472

Quote:



Originally Posted by *Burn*

@ Lando, I ran some ATTO and speed tests that saw my top seek and random read speeds when I first installed and formatted the array, several months later I re-ran them and saw a drop in performance, not that much, but a little bit off the top. I don't know if this could be due to more programs installed or not, perhaps due to defragging.


That's totally expected though. No defrag program in the world can be as effective as a fresh install. Also, programs installed on the outer part of the platter will perform ever so slightly faster than programs installed further in. (higher angular velocity)


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## maxflavian

Quote:



Originally Posted by *sccr64472*


That's totally expected though. No defrag program in the world can be as effective as a fresh install. Also, programs installed on the outer part of the platter will perform ever so slightly faster than programs installed further in. (higher angular velocity)


Tsl Tsk....The angular velocity is constant accross the whole platter, it isn't higher towards the edge !!


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## gonX

Quote:



Originally Posted by *maxflavian*


Tsl Tsk....The angular velocity is constant accross the whole platter, it isn't higher towards the edge !!


Well, he is partly right, but it's the inside of the platter than gives highest burst speeds.
BTW. Way to bump an old thread


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## ENTERPRISE

Im no RAID expert however one thing ill tell you is that if you want the best defragmentation and Information about fragmentation and a good graphical representation you will want to use Diskkeeper 10 here mate..Destroys Windows defragger.

Diskkeeper 10: http://www.diskeeper.com/landing/lan...FSE7GgodYzFl2g


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## Wincet

How does someone's first post bump an 8 month old thread???


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## maxflavian

Quote:



Originally Posted by *Wincet*


How does someone's first post bump an 8 month old thread???
























why not?


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## sniperscope

This is a decent thread, bump for the info


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## CravinR1

I defragmented my Raid 0 right after performing some benchmarks, then after the format did some benchmarks ....... got the same.

I guess it was cause the benchmarks wasn't using the data on my drive but my drive's read/write capabilities


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## Proof

I use O&O Defragger on my RAID 0 setup and I was wondering if that is the best program or if there is a better one what is it? Window$ Vi$ta Ultimate x64.


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## rymn

Quote:



Originally Posted by *Lando95*


I think what he is saying is that Windows only detects 1 logical drive, and the raid controller does the rest.


That would have been my guess..


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