2012-08-13 08:51 AM
We have a VMware datastore configured on our FAS2240. I'm getting an alert on our monitoring system due to usage of a particular volume. The volume in question shows 86% utilised and the LUN at 97% within System Manager, this is also reflected within VSC. However, the datastore itself, i.e. what VMware is seeing, is only 31% used.
My question is, why would there be such a difference between these figures? Is there any way to tell what is utilising this space? There are no snapshots in play.
We have other volumes configured in the same way with similar VDI load and there is nowhere near as much difference between these figures.
2012-08-14 11:55 AM
check whether there are couple of other LUNs carved out from the same volume.
check the snap reserve on volume
check if there are any snapshots taken at LUN level.
2012-08-15 01:48 AM
The Fractional Reserve setting is disabled by the looks of it.
Here's the output of the df -r command.
FAS2240-02> df -r
Filesystem kbytes used avail reserved Mounted on
/vol/vol0/ 199229440 3880512 195348928 0 /vol/vol0/
/vol/vol0/.snapshot 10485760 237508 10248252 0 /vol/vol0/.snapshot
/vol/v_vdi_datastore9/ 432402476 186069996 246332480 0 /vol/v_vdi_datastore9/
/vol/v_vdi_datastore9/.snapshot 0 0 0 0 /vol/v_vdi_datastore9/.snapshot
/vol/v_vdi_view_datastore9/ 70265404 12336924 57928480 0 /vol/v_vdi_view_datastore9/
/vol/v_vdi_view_datastore9/.snapshot 0 0 0 0 /vol/v_vdi_view_datastore9/.snapshot
/vol/v_vdi_datastore10/ 432402476 384968280 47434196 0 /vol/v_vdi_datastore10/
/vol/v_vdi_datastore10/.snapshot 0 0 0 0 /vol/v_vdi_datastore10/.snapshot
/vol/v_vdi_view_datastore10/ 70265404 11059304 59206100 0 /vol/v_vdi_view_datastore10/
/vol/v_vdi_view_datastore10/.snapshot 0 0 0 0 /vol/v_vdi_view_datastore10/.snapshot
2012-08-15 03:08 AM
Fractional reserve isn't to be blamed, indeed.
OK, let's go back to basis. You said this in your original post:
The volume in question shows 86% utilised and the LUN at 97% within System Manager, this is also reflected within VSC. However, the datastore itself, i.e. what VMware is seeing, is only 31% used.
First of all, volume is utilised, because there is LUN in it, which is space-reserved - it doesn't matter is not filled with data. Secondly: where are you getting the info the LUN itself is 97% full - System Manager GUI?
VMware is seeing the LUN, not the volume, so is reporting space utilisation (presumably correctly) within the LUN.
2012-08-15 04:30 AM
Thanks for the response.
That makes sense that the volume is utilised because a LUN is stored within it. I'm seeing the 97% LUN utilisation within System Manager and also the Virtual Storage Console plugin for VMware vSphere, which is where the below screenshot is from.
As can be seen, the Datastore usage (what VMware see's) is only 52%, yet the LUN usage is close 98%, that is what is baffling me.
2012-08-15 04:57 AM
Has this particular datastore been thick provisioned on VMware? Maybe LUN usage shows a simple fact VMware filled the LUN with zeroes during formatting?
2012-08-15 08:30 AM
Not that I'm aware of, I didn't know there was a way within VMware, the volume is definitely Thin Provisioned within the NetApp side of things. I think I'll just shuffle some of the Virtual Machines around and keep an eye on it. It's very strange though.
2012-08-15 08:46 AM
Have a look at this for more details re provisioning on the VMware side:
Basically so called Eagerzeroedthick VMDK can give this result - all of the allocated space is zeroed out at creation time.