Is a SAN defragmentation worth it?.
Hi,
We have a two node Windows cluster which is attached to a SAN. We've made a RAID 5 on that SAN. The case is that Microsoft has suggested us doing a SAN defragmentation and we're hesitant. I'm quite sure that a defragmentation is very useful on a laptod, for instance, but not that much with a SAN system.
In the case that we do the defragmentation, what's the best application for that purpose?. Taking into account that we have over 5 TB of data and 1 TB of free space, how long will take to do the defragmentation?, do we have to stop any activity?.
Thank you very much.
We have a two node Windows cluster which is attached to a SAN. We've made a RAID 5 on that SAN. The case is that Microsoft has suggested us doing a SAN defragmentation and we're hesitant. I'm quite sure that a defragmentation is very useful on a laptod, for instance, but not that much with a SAN system.
In the case that we do the defragmentation, what's the best application for that purpose?. Taking into account that we have over 5 TB of data and 1 TB of free space, how long will take to do the defragmentation?, do we have to stop any activity?.
Thank you very much.
SOLUTION
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Be very careful, if your SAN uses thin provisioning a defrag may cause a thin partition to become fat.
SAN degrag is not a good idea, will not save much out of it.
You may need to do it if you are going to gain lot space from the defreg.
comming to your question, 5 TB degrag may take more than 72 hours.
Yes, perforemance will degrade in Raid5 , when you do defrag, no need to stop any apps .No down time required .
In worst case if a disk failed during the defrag , it may write the errors to the rest of the disks, that cause multi disk failure.
Defrag is best in thin provision, than in thick provision.
Lastly, What type of storage you use?.You may not be able to stop the defrag in some vendor's storage arrays once you start it , so follow the storage vendor recommendations for defrag than Microsofts.
You may need to do it if you are going to gain lot space from the defreg.
comming to your question, 5 TB degrag may take more than 72 hours.
Yes, perforemance will degrade in Raid5 , when you do defrag, no need to stop any apps .No down time required .
In worst case if a disk failed during the defrag , it may write the errors to the rest of the disks, that cause multi disk failure.
Defrag is best in thin provision, than in thick provision.
Lastly, What type of storage you use?.You may not be able to stop the defrag in some vendor's storage arrays once you start it , so follow the storage vendor recommendations for defrag than Microsofts.
ASKER
Hi,
Sorry for the delay, I was on holidays.
We have a EMC Clarrion CX500.
There is only a two node Windows 2003 cluster server attached to the SAN. We also have another server but it's only giving service as a print spooler with a bit of activity and it's going to disappear in a few weeks.
There are two RAID 5 storage groups, the first one is attached to the print spooler, and the second one is attached to the cluster.
The cluster storage group is made of one Meta LUN and three mote LUNS. The Luns has been added as needed.
For thos who say that defrag is not recommenden, I've read some articles even from EMC saying just the other way around.
I don't want to do a defragmentation to get free space, I only want to get better performance. But before that, I'm doing some tests with Iometer. Does anybody have some benchmarks with this tool?.
Thank you.
Sorry for the delay, I was on holidays.
We have a EMC Clarrion CX500.
There is only a two node Windows 2003 cluster server attached to the SAN. We also have another server but it's only giving service as a print spooler with a bit of activity and it's going to disappear in a few weeks.
There are two RAID 5 storage groups, the first one is attached to the print spooler, and the second one is attached to the cluster.
The cluster storage group is made of one Meta LUN and three mote LUNS. The Luns has been added as needed.
For thos who say that defrag is not recommenden, I've read some articles even from EMC saying just the other way around.
I don't want to do a defragmentation to get free space, I only want to get better performance. But before that, I'm doing some tests with Iometer. Does anybody have some benchmarks with this tool?.
Thank you.
ASKER
Any answer?.
ASKER CERTIFIED SOLUTION
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ASKER
I guess the defrag process won't end up on Monday morning. If I kill the defrag job on Monday morning, Will I lose all the work done or I'll be able to continue from that point?.
Thank you.
Thank you.
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my 2 cents
worked with a client that also had a 5tb volume with 4tb of data.
data was almost all 50k jpgs created by an imaging application
backup throughput was worse than awful
tried everything finally under Microsoft's recommendation we defrag'd
had to stop it a few times but it took a month yes a month before it was finally done
result was way better than we expected
so based off some real world experience I gotta join the yes to defrag camp
worked with a client that also had a 5tb volume with 4tb of data.
data was almost all 50k jpgs created by an imaging application
backup throughput was worse than awful
tried everything finally under Microsoft's recommendation we defrag'd
had to stop it a few times but it took a month yes a month before it was finally done
result was way better than we expected
so based off some real world experience I gotta join the yes to defrag camp
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a good thing about contig is it can be used to do selective defrag
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ASKER
Thank you so much for that quite interesting and useful posts.
I installed diskeeper a few days ago, so I'll try first with diskeeper and later I'll do some tests with sysinternals tool.
By now, My intention is only to better disk performance, I'm not interested on get free space as there is a lot of it left.
I'll give you news about the defrag during the weekend.
Thank you again.
I installed diskeeper a few days ago, so I'll try first with diskeeper and later I'll do some tests with sysinternals tool.
By now, My intention is only to better disk performance, I'm not interested on get free space as there is a lot of it left.
I'll give you news about the defrag during the weekend.
Thank you again.
ASKER
I have received an alert from this question as it was abandoned, but I'm still waiting for an expert answer.
I'd like to close this question asap.
Thank you.
I'd like to close this question asap.
Thank you.
So what is wrong with response #26313429 ?
Or if you are concerned about defrag, run the contig program to see which files are the most fragmented. Choose a rather large and fragmented file, benchmark I/O thoroughly, then use contig to just fix that one file, and run benchmarks again. If it is faster, defrag everything. If it is slower or no change, leave things alone.
I would check with you vendor for their best practice on it. In my case with the SAN i have the data is virtualized accross all disks, rather than just a group of disk in a raid group.