free Space in OnCommand and ESXi different

[rene04]

Hi,

we have a NetApp FAS8020 (NetApp Release 8.2.2P1 7-Mode). In OnCommand Manager i see that Volume, lets call it Volume X, with 43% used space.

Total Space: 2,1 TB

Available Space: 1,14 TB

then, when i look at the LUN which is on that volume i see 62,31% used space.

Total Space: 2 TB

Available Size: 771,79 GB

AND in our NAGIOS i see:

value from ESXi 6.0:

Filesystem netapp_ds10

WARN - 82.8% used (1.66 of 2.00 TB), (warn/crit at 80.00/90.00%), trend: 0.00 B / 24 hours, uncommitted: 0.00 GB, provisioning: 82.8%

So, what information is correct? Why is:

- on the NetApp Volume and Lun different?

- on NAGIOS completly different?

I must say that NAGIOS is getting this value from ESXi 6.0. When i check directly the NepApp with NAGIOS i get this:

value from NetApp directly.

Filesystem /vol/vol_vm_c1derz01_ds10/

OK - 42.9% used (877.07 GB of 1.99 TB), trend: +1.42 GB / 24 hours

Can some please explain to me why and if this is fixable somewhere?

regards,

rene

[sgrant]

Hi Rene, I realise it's a little late, however been thinking about this...

From your output when NAGIOS reports against the volume is sees the same 43% used figure as OnCommand, so no issue there...we have a 43% used volume on the storage.

However, we do have the LUN showing more space than the volume...I believe this discrepancy is explained by Storage Efficiencies in thin provisioned block environment, i.e. LUNs.

VMware datastores dedupe very well; if for example the datastore in ESX is thick provisioned, i.e. it's been zero'd out, or has many VMs of the same OS, etc, then on the storage then these blocks will be mostly deduplicated. These savings will be shown in the volume capacity, but not the LUN.

Example: I have a test LUN with no snapshots...

test_lun	thin provisioned	3.92GB available	1.08GB Used	5GB total size
test_vol	thin provisioned	5.12GB available	0.3GB Used (much smaller!)	5.15GB total size

Volume Efficiency Savings in this example are:

• Dedupe savings 1.04GB
• Compression savings 13.57MB
• Total savings 1.05GB

We have 1.08GB used space in the LUN, however only 0.3GB used in the volume. However, if we add the total savings from the Storage Efficiencies to the volume used space it gives 1.08GB i.e. the used space in the LUN. You will be able to see the deduplication/compression savings for the volume using the command df –S or the Storage Efficiency tab for the Volume in System Manager.

However, that does not explain why ESX can see more used space than OnCommand. This could be down to any VM snapshots reserving additional space, or VM bug 2110199, fixed in 6.0 Update 1a.

If these were NFS datastores then both ESX and OnCommand would report the same capacity.

Hope this clarifies the figures for you.

Thanks,

Grant.