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November 4th, 2013 13:00
PPMS vs SAN COPY for windows 2003 clusters
HI,
I have two more clarrion arrays to go for the Array refresh project. I can see the goal post as I have 5 more cluster groups to do on one of the arrays. They are a two node and five node windows 2003 cluster. I know I cannot migrate the quorum, so what is the advised method, SAN copy or PPME? I am migrating to a VNX.
Thanks in advance!
Admingirl
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dynamox
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November 4th, 2013 14:00
if they are ok with complete downtime you can SAN Copy the quorum drive as well. It's tiny so you can setup your session after both nodes are offline. Windows clustering 2k3 uses disk signature to identify drive letters/cluster resource ..since you are not changing servers but simply swapping LUN, it will not know anything happen. I like to keep host ID the same between source and target array.
dynamox
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November 4th, 2013 13:00
since these are win2k3 clusters and not win2k8 clusters (where you are required to take failover group offline to commit unless you are running PowerPath 5.1 SP that supports online commit) i would go with PPME ..don't have to take cluster offline. As you know there is host CPU overhead but it's typically very negligible and you can throttle the speed.
admingirl
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November 4th, 2013 13:00
Thank you Dynamox! The only thing the windows team is concerned about is in the two node cluster, one of the nodes is not healthy. I told them they have to recreate the quorum and they are a bit squimish. Would SAN copy allow for the quorum to be migrated, also does SAN copy keep the drive letter? I would really be more comfortable using PPME.
admingirl
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November 7th, 2013 12:00
It might be best to use PPME, however, I have one additional question. The five node cluster has 37 luns. They are not all large, however, I checked the white paper for PPME hostcopy and did not see what or if there is a lun limit. If I missed it I apologize.
dynamox
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November 7th, 2013 12:00
i just looked at PPME admin guide and can't find any session limitation either, since this is host based copy and it still running win2k3 (must be old boxes) i would be conservative and start out with a few session and watch CPU. Are any of those LUNs > 2TB ?
christopher_ime
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November 8th, 2013 15:00
Unlike Open Migrator which as a hard limit of 10 sessions at a time, for PowerPath/ME while there is a LUN limit it has more to do with the definition of the variable used for the session ID but at the software code level. I've seen reference to 30,000+ but you'd exceed other maximums let alone performance concerns before you come close to exceeding it so consider it more theoretical.
For instance, there are maximum session limits if using OR, even techType=hostcopy you'd be up against OS, HBA, SP port, initiator record (paths), storage group limits, etc. Then of course there would be the concern about the resources consumed on the host itself especially in consideration of hostcopy.
admingirl
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November 15th, 2013 07:00
Thank you Dynamox, no, thankfully no 2TB luns.
Thanks again!
Benita
dynamox
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November 15th, 2013 14:00
good, there is a bug in PowerPath 5.5 or 5.7 (can't remember exact version) where if LUN is > 2TB as soon as you start PPME session it blue screens the box ..need to upgrade to the latest 5.7 (SP1 i think) prior to using PPME.