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Metalun expansion question
I have a question with regards to expanding a metalun and what the best option would be. Currently the metalun is composed of 4 luns from 4 different Raid 1/0 groups. Each raid group contains 8, 133GB, FC drives. I will soon be adding a DAE to the array since we are completely out of capacity. The drives we are adding are 300GB FC drives (same rpm speed as the others just different capacity). These additional drives will be used in the expansion of the metaluns. I am not sure which route to go with regards to adding these drives into the existing environment. Should I use the additional drives and expand the existing raid groups or should I create new raid groups and then concatenate to the existing metalun? Performance is not the main objective here as it currently is adequate; capacity is the main concern.
sure, there is overhead with restriping but if you say application is not performance sensitive, i would set priority to medium and let it chug alone. Do you know why this was built using 1/0 if it's not performance/write intensive ?
If performance is a concern, you certainly do not want to concatenate. Also, if you plan to expand the metalun onto the new drives, if you create more LUNs on those new drives, you could start to have contention. I think the best solution would be to find out what the I/O requirements are for the application. If you can stand longer rebuild times and a if a 10+1 (or more if the db will grow) RAID5 can support the IOPs, I would carve that and use PPME to migrate to the new LUN.
dynamox
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Posted October 18th, 2011 12:00
definitely don't want to extend existing raid groups as you will be wasting half of your capacity. Only half of your 300G drive will be used in a raid group built from 146G drives