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August 6th, 2012 10:00
CX4,AX,VNX, maxium changing multiple failed disks at the same time - without impact production
hello need a list how many disk can ben changed without impact production,
i need the best practice, for instance i have 5 failed disk and only 3 hotpares in active status
replacing only 3 of them.
having in my hands the total of 5 replenishment, can i replace all of them at the same time.
or there is a maxium limit.
Position of disks, type of RG, priority of rebuild, must be check first before the replacement,
but, is there any complete list for all models? in order to not impact production,
following best practices?
thank you
MC.
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AnkitMehta
1.4K Posts
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August 6th, 2012 10:00
Scenario 1:
If the drives faulted are in different RAID Groups:
Total Drives Faulted: 5
Hot Spare Invoked: 3
We can replace all 5 at the same time 3 will rebuild from Hot Spare and other 2 will rebuild the data from Parity.
Scenario 2:
If the drives are faulted in the same RAID Groups:
SP Collect Analysis is required for the proper action plan depending what RAID Type was used and other factors.
However, coming back to your question: Yes, it will impact the performance of the storage system depending on the rebuild priority is set.
A LUN rebuild is a prioritized operation on the Storage System (SP). The available priorities are: ASAP, High, Medium and Low. Low, Medium and Hight priorities have little effect on the performance of production workload where as ASAP priority compeltes a rebuild in the least amount of time but it may have an adverse effect on the performance.
This is the same for all the CLARiiON Family Models.
For Best Performance Practices you may refer to Knowledge Base Article: emc218359 and EMC CLARiiON Best Practices for Performance and Availability.
AnkitMehta
1.4K Posts
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August 6th, 2012 12:00
No Problem. Just trying to be helpful
jelucho
295 Posts
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August 6th, 2012 12:00
good. and clear to me.
thank you.
mc
jelucho
295 Posts
0
August 6th, 2012 12:00
excelent!
if all of them have ASAP or HIGH allready set.
where the impact is showed,
on
SP utilization,?
LUN writes and reads SAN side?
LUN writes and reads HOSTs side?
will SP Cache exceed HW or LW during rebulding time?
or simply it will not be perceptible to the customer only if measured by analyzer?
thanks.
MC.
AnkitMehta
1.4K Posts
1
August 6th, 2012 12:00
To my knowledge if you are talking about 5 drives rebuilding with ASAP Priority, LOL you would not even have to bother to check anything you will get a support call in few mins that application is slow, or etc.
However, yes as I mentioned earlier rebuilding is a prioritized operation on SP so SP Utilization will be High. (Very High in case of 5 drives rebuilding with ASAP Priority, **Don't do that, ever**)
SAN performance is impacted in rebuilding process, so whatever impact will be there it will on the SAN side.
As far as HW & LW is concerned, NO they are dependent on IOPS (SP Cache) not SP Utilization! :|
Refer to Watermark section on the document I have mentioned above.(Page Number 99 Onwards)