SimpliVity and SDelete

[MrStarleaf]

Hello.

If I want to use SDelete with -z,  I have understood that -z will do so that the 100% of the provisioned disk space will be used.  So if you have 2TB disk it will use 2TB in VMWare for the time it takes to run SDelete, but it will give it back later.

But how will it affect the SimpliVity Nodes physical disk space?

Why I'm asking  for we have lite of physical space and want to run it to reclaim physical diskspace from VM:s..
Will i take 2TB from the Nodes physical disk space under the process, or will deduplication and compression just ignore the zeros. So it will not affect the space on the nodes.

[Brian_Galante]

I use sdelete, and it has been a life saver. 

I had a DBA who was backing up her DB's like it was 1999. She was doing a dump to a local drive on the same server every night (Over writing the old one), and this slowly ate up all the Simplivity space due to the backup process not writing to the same exact blocks on the filesystem.

When you run sdelete like this: "sdelete -z d:" to zero out the D drive what will happen is:

The actual D drive in windows will appear to fill up while sdelete is running. Don't panic! It will release the space and will not impact running applications on that drive. 

You wont see the reclaimed space for up to 24 hours in both the simplivity physical space or in VMware "Storage Usage" of a VM. (Both pics attached) These will both take up to 24 hours to reflect the reclaimed space.

[MrStarleaf]

That sounds great, but my fear is that the physic diskspace on the node will hit the ceiling under the SDelete process.

For as an example,  If you have 1TB left on the node in physic diskspace. And you have a VM with 2TB logic diskspace, and you are using 1TB of that space. Is it any risk that while you're using the SDelete -z on the VM disk, the node will hit the ceiling of its physic capacity?

Or will the Node understand that the 0's that are written are not any data, so it will not use any physic space on the node?

[Brian_Galante]

I would think with dedup and compression in force you should be good.

Something else you can look at is, the free space by host, because the number you see in Vsphere is for the cluster as a whole. Login to the OVC and run "dsv-balance-show --shownodeip" to see the free space by host. 

If you can put the VM on a host that has enough free space, that would help ease any anxiety.

You can rebalance the hosts too to make enough room on one host.

You can also mount an external NFS share on a NAS and move a vm or two there temporarily while you clean up.

[Marcel_I]

Hi MrStarLeaf,

We are in a similar situation and would realy like to know what the impact is on the SimpliVity storage. Were you able to test and monitor this? 

Thanks,

Marcel

[MrStarleaf]

Hi Marcel.

I have tested and did not see any changed raw disk usage. On the OVC:s.
But maybe you can't see the changed disk usage. Directly from the Cli command.

I used it carefully and have not encountered any problems so far.  As mentioned up here, dupe should take care of the 0 that are written on the VM disk to reclaim free space.