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Adding disks to existing aggr - reallocate questions

strattonfinance
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Hi all,

Hoping the NetApp community can provide some assistance to this relatively novice NetApp administrator.

Firstly, to describe the environment / scenario:

- FAS2050 running DOT 7.3.5

- Head #1 (which this question relates to) has all 20 "internal" disks assigned to it

- Currently, 16 of these 20 disks are in a single aggregate, all in a single RAID-DP raid group. This aggregate is c. 90% full at present.

- This aggregate contains a bunch of flexvols used exclusively to store VMDK files for our VMware environment (provided over NFS), and has both snapshots and deduplication enabled on all volumes.

- Out of the remaining 4 disks, 2 are hotspares and 2 are not being used at all (freed up after some recent changes involving head #2)

- We want to add the 2 "unused" disks to the existing raid group / aggregate, increasing the raid group size to 18 in the process.

I understand that we will need to run a "reallocate" after adding the 2 extra disks to the existing raid group / aggregate or else we will end up with "hot spots" on these new disks.

From some research it appears that we need ensure DOT only does a physical redistribution of the blocks across all disk in the aggregate and does not try to otherwise rearrange them, otherwise we risk "un-deduping" our deduplicated data and/or greatly increasing the space consumed by our snapshots. Both of these would result in big problems for us as we'd rapidly run out of space in the aggregate - we need to perform the physical reallocation across the new disks without increasing space usage.

Therefore, what I need help with is: Again from research I think what we need to do is run "reallocate start -f -p <volume_name>" against each volume in the aggregate, but I'm not sure. Can anyone confirm if this is correct, and provide the correct syntax if it is not?

Also, a bonus question: I'm assuming the reallocate will put a significant load on our filer and hence should be run outside of peak hours. Can anyone give some (broad) guidelines as to how long we can expect a FAS2050 to take to reallocate c. 1.6TB of data across the newly-expanded 18-disk RAID-DP group (144GB 15K drives if it matters), assuming no other load on the filter?

Thanks!

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