Microsoft quorum and exchange LUN migration

Question

Hi,
I want to migrate 2 LUNs, because now they reside on the Vault disks. These 2 LUNs are used for Microsoft cluster quorum disk and exchange information store. I was thinking about using lun migration to move them to new raid group, but since both are sensitive applications I'm worried of any downtime during the migration. I was making upgrade of the FLARE recently and at the end when the primary SP was starting Exchange lost its information store because the LUN is on the Vault drives.
I'm wondering is there any performance degradation or higher response time to the host during the migration process ?

amrith · Answer

I had a lun migration sometime back for a lun which was used by a Exchange server and they never complained of performance during that period .May be do it at non-peak hours which will help further ,

RRR · Answer

I've played around a bit with this and I've noticed the following:
HIGH means 3MB/s = 10GB per hour, but pperformance impact can be noticible
ASAP = means as fast as the Clariion can go and this will have an impact. the speed I noticed was 120MB/s (not 350 as mentioned in the white paper) on a RAID10 (3+3) set of 15k drives to a new empty RAID10 (3+3) set of 15k drives.
LOW means really really slow and this means a migration can take up to days or even weeks, but impact is low as well. I doubt you will even notice it.

mpi2 · Answer

Hello,Lun Migration is the best choice for your situation.You can consider two ways:-) make the migration after midnight (or whenever you can afford a performance degradation) with 'ASAP' setting.-) make the migration during the day doing with 'low' priority. With this setting you should not see any performance impacts.You can search for the Whitepaper 'The Influence of Priorities on EMC Clariion LUN Management Operations' on powerlink where you get detailed information of priority settings and the duration of migrations.Best RegardsManfred

bstoyanov_393481 · Answer

Ok, this is for the copy operation between the LUNs. How about when it is time for the second LUN to become as the source ? Could this transfer lead to exchange downtime ?

RRR · Answer

The white paper mentioned is a real good one

RRR · Answer

No downtime at all. It's all on the fly ! The so called new LUN becomes the identity of the old LUN. The 'new' LUN's identity is only temporary. During the migration the 'new' LUN will be hidden and when the migration is done, it's gone.So 'from the outside' you don't even know any difference, except perhaps performance. And yes, you can do this without any downtime at all.

bstoyanov_393481 · Answer

Yes, thats what white papers says. In the documentation and the upgrade is without downtime, but in fact we had downtime with exchange

RRR · Answer

Ok. There will be no downtime as far as the storage is concerned. At least, there should be no impact at all. If it did happen, there must have been another issue as well that caused the downtime.

I'm wondering is there any performance degradation or higher response time to the host during the migration process ?

Response times are slighty higher, but that can be tuned. The white paper "The Influence of Priorities on CLARiiON LUN Management Operations" clearly mentiones the possibilities.

CLARiiON

Microsoft quorum and exchange LUN migration

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