SSY-V: speed up disk removal from pool

Sooner or later there will be the requirement to remove a physical disk from a DCS disk pool. The default way to remove such a disk is to idetify the disk (this is probably the most challanging moment in the whole process), right click on the disk and select "Remove from disk pool"

 

remove pooldisk01

 

DC then automatically starts to move used SAUs to other disks in the pool. During this removal process, the disk will stay in the pool and looks like any other disk but if you look at the details of the disk you will see:

 

 

remove pooldisk02

 

The state is "Removal" and below you see the remaining MB/GBs to be moved from the disk. During the removal process the disk is marked for removal and therefore no new SAUs can be allocated from this disk. Existing ones can still get accessed in the normal way. The process is compareable to VMware's maintenace mode where the host is marked to go to maintenance and running VMs are planned to be moved to other hosts in the cluster but still remain available.

Since the removal process is a low priority task this removal procedure can take a long time, depending on the amount of data to be moved.

To speed up things a bit there is a fully supported way:

  • mark the disk for removal as seen before
  • check which vDisks use SAUs from this disk. This can be done either on the Powershell or you can simply take any vDisk on the pool because SSY-V stripes data from each vDisk over each physical disk in the pool as long as your settings (like AutoTiering and tier class affinity) allow it.
  • Now take these vDisks, right click on them and select "Move". Choose the DCS and select the same pool as the vDisks already are located on
  • SSY-V will now check what to do: as the vDisks are already on the given pool it will check if any of the pool pDisks are marked for removal. Because SSY-V is not allowed to use any SAUs from these disks it will move the SAUs on the marked disks to other disks in the pool. But this time, the process is a high priority process and things get faster.

This procedure can also help you in situations where the automatic removal process left some SAUs on the pDisks. This happened sometimes in our labs and it was worth a try to do the "manual" way as described right before.

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