You are spot on, use the unmap tool to reclaim space on the LUN. Compellent thin provisions everything on the back end and depending on your environment, you should probably be thin provisioning your LUNs on the VMware end. Over time as you delete servers in VMware and vmotion from datastore to datastore that space will not be reclaimed on Compellent b/c the storage is ignorant of the fact the data is no longer being used. The 'fix' for this until there is complete integration between VMware and Dell is to run that unmap tool. What we started doing every quarter or so is to run the unmap tool on all LUNs that are thin provisioned (in our environment that is all volumes). I've tested unmap multiple times and I have had no issues with running the tool while servers are running on that volume. I would suggest running the tool on a server that doesn't have a lot of workload because the CPU does spike during the unmap period (datastore reads will spike as well). As for backups and snapshots I have no issues with space regarding those. Replays will freeze blocks of data for reference, but once that replay is expired the space is recouped. Regarding backups it depends on what you are using for backups - we use CommVault which will take a snap of the LUN, copy the data off then release the snap (so for a short period of time there is space eaten up during the backup but it takes only a few minutes to copy off the data).
Hi guys, I'm installing a new storage Dell Compellent SCv2020 with vSphere 5.5 U3b for an existing customer I have deep knowledge of Dell PowerVault storages but I'm new with Dell Compellent. I've read that making snapshots for backups or running Storage vMotion can affect free space on the storage due to native LUN thin provisioning: communities.vmware.com/.../436628;tstart=0 The suggestion is to manually run or schedule the command "esxcli storage vmfs unmap -l MyDatastore" that invokes the SCSI UNMAP primitive I've tested a Storage vMotion and indeed the space on the source LUN remain allocated until manually "unmapped". I've not yet tested how backup snapshots affect the free space on the storage because I've not yet migrated any VM on the new infrastructure (by the way I will use Veeam Backup v8 that heavily rely on VMware snapshots) Anyone here can share ideas and feedback? Many thanks guys Marco
Compellent free space reclamation