AranH: why would you set the prio before starting the defrag ? You can switch defrag priorities when the defrag is running, so if you want set it to low during the day and to medium during the night. There's no need to set it in advance.
Because a lot of people just start the defrag and forget about it. If you set the priority on the RAID group that you intend to use for the entire defrag then you don't need to worry about it after that.
Changing the settings would also require you to wake up before your business starts, connect to your corporate network and change the defrag priority before it can impact your business. For people that support businesses that span multiple time zones that is not reasonable. I am not going to wake up at 4am just to change the setting for a defrag. I would would rather set it once and let it run.
My experience is that if you set the rate to low you will be waiting several days for the defrag to complete. The low setting is designed to not impact production performance. I believe the defrag to be pretty safe and have never experienced or heard of anyone having problems with it. In fact what I usually do is defrag one raid group at a time but set the rate to high so I can guarantee it finishes before the morning.
If you want to be safe I would look to see if there are any FLARE patchees released which address issues with defrag. I do not know of any but take a look.
dl, LUN access by hosts is not interrupted by a defrag, so whether it is a metaLUN or stand alone LUN you should not have an issues with the defrag. Since you are not under any time constraints using the Low setting is definitely your best option. Just remember to set the defragmentation priority on the RAID group before selecting the defrag button.
As far as your corruption concerns, I have never heard of or experienced myself any corruption of a LUN as a result of defragmenting a RAID group. It is a standard maintenance process on CLARiiON arrays and has been a solid feature for quite a while now.
There is no need for concern in my opinion. Set the priority to Low and defrag your groups one at a time.
When we are defragging for cleanup and don't need the space any time soon we always set to low and let it take it's time. We never notice an impact to performance (which is what the low setting is designed for).
We have also never experienced any kind of corruption due to defrags. And I have done a LOT of defrags over the years!
Being still new at this forum, I'm am still trying to control the Helpful/Correct postings. Just noticed there are points assigned according to "helpful" or "correct". In my opinion the responses were all very much worth 10 points, but alas, I have voided any opportunity to do this right thing. In any event, we will forge forward with the defrag. We started one today at low priority on the least active raid group. Yep, it's pretty slow, but, thanks to the responses to this thread, we have no fear of performing the function and time is not an issue.
3. Start the defrag process to run over the least active time periods
Since the defrag will run for days, you cannot run it over the least active time periods. Perhaps a weekend can be considered as such ?
AranH: why would you set the prio before starting the defrag ? You can switch defrag priorities when the defrag is running, so if you want set it to low during the day and to medium during the night. There's no need to set it in advance.
Message was edited by: RRR
Added AranH's name to point out that this part was meant for him
Not to mention the fact that it is always a best practice to know what you are doing before you do it. What if for some reason the RAID group had been set to High defrag priority in the past. If you didn't check before you started you could be affecting users before you know it.
For things like this I never like to assume I know that the settings are right. I always check before proceeding.
AranH1
2.2K Posts
0
September 18th, 2008 07:00
AranH: why would you set the prio before starting the
defrag ?
You can switch defrag priorities when the defrag is
running, so if you want set it to low during the day
and to medium during the night. There's no need to
set it in advance.
Because a lot of people just start the defrag and forget about it. If you set the priority on the RAID group that you intend to use for the entire defrag then you don't need to worry about it after that.
Changing the settings would also require you to wake up before your business starts, connect to your corporate network and change the defrag priority before it can impact your business. For people that support businesses that span multiple time zones that is not reasonable. I am not going to wake up at 4am just to change the setting for a defrag. I would would rather set it once and let it run.
dlamar1
9 Posts
0
September 17th, 2008 09:00
-dl
aaronj1
35 Posts
1
September 17th, 2008 09:00
If you want to be safe I would look to see if there are any FLARE patchees released which address issues with defrag. I do not know of any but take a look.
-Aaron
AranH1
2.2K Posts
1
September 17th, 2008 09:00
LUN access by hosts is not interrupted by a defrag, so whether it is a metaLUN or stand alone LUN you should not have an issues with the defrag. Since you are not under any time constraints using the Low setting is definitely your best option. Just remember to set the defragmentation priority on the RAID group before selecting the defrag button.
As far as your corruption concerns, I have never heard of or experienced myself any corruption of a LUN as a result of defragmenting a RAID group. It is a standard maintenance process on CLARiiON arrays and has been a solid feature for quite a while now.
There is no need for concern in my opinion. Set the priority to Low and defrag your groups one at a time.
Aran
Allen Ward
4 Operator
•
2.1K Posts
0
September 17th, 2008 10:00
When we are defragging for cleanup and don't need the space any time soon we always set to low and let it take it's time. We never notice an impact to performance (which is what the low setting is designed for).
We have also never experienced any kind of corruption due to defrags. And I have done a LOT of defrags over the years!
dlamar1
9 Posts
0
September 17th, 2008 16:00
Just noticed there are points assigned according to "helpful" or "correct". In my opinion the responses were all very much worth 10 points, but alas, I have voided any opportunity to do this right thing.
In any event, we will forge forward with the defrag.
We started one today at low priority on the least active raid group. Yep, it's pretty slow, but, thanks to the responses to this thread, we have no fear of performing the function and time is not an issue.
Thanks for all the responses.
-dl
RRR
4 Operator
•
5.7K Posts
0
September 18th, 2008 02:00
RRR
4 Operator
•
5.7K Posts
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September 18th, 2008 02:00
Since the defrag will run for days, you cannot run it over the least active time periods. Perhaps a weekend can be considered as such ?
AranH: why would you set the prio before starting the defrag ?
You can switch defrag priorities when the defrag is running, so if you want set it to low during the day and to medium during the night. There's no need to set it in advance.
Message was edited by:
RRR
Added AranH's name to point out that this part was meant for him
Allen Ward
4 Operator
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2.1K Posts
0
September 18th, 2008 09:00
For things like this I never like to assume I know that the settings are right. I always check before proceeding.