#vmware Virtual Volumes (#VVols) – Syslog and Scratch Usage

VVolsI had a very interesting query in my recent VVol post on vSphere HA interop. In that post I showed how the VVol datastore could be used for datastore heartbeating. The question then arose when the VVol datastore could be used for other things, such as a syslog and scratch destination. I couldn’t see any reason why not, but just to be sure, I tested it out in the lab. The quick answer is yes, you can use a Config-VVol for syslog, and no, you cannot use a Config-VVol for scratch. If you want to see the steps involved, and what happens when you do set a Config-VVol as the destination for these features, please read on.

Setting up syslog to point to a VVol datastore

The first step is to create a Config-VVol on the VVol datastore. If you want to know more about a Config-VVol, and other VVol types, types of VVols are covered in this post here. It is straight forward to do and can be done by creating a new folder on the VVol datastore from the vSphere web client. On my VVol datastore, I create a new folder/Config-VVol called logs-and-scratch, and then a sub-folder named after each of the two hosts that were sharing the datastore (h09 and h11). A screen shot shows the contents below:

syslog.2Once the folders were created, it was simply a matter of changing the Advanced Settings for syslog (syslog.global.logDir) on each of the hosts, and have them point to the folder on the VVol datastore.

syslog.3Once the changes have been made, we can immediately observe the log files from the hosts being created on the VVol datastore. Pretty simple to do, and it seems to just work.

syslog.5 Setting up a scratch location on the VVol datastore

The next step was to set the scratch location on the VVol datastore. This follows the same steps as syslog, more or less. We will use the Config-VVol created earlier, which we called logs-and-scratch. In each of the hosts sub-directory, I created a folder called .locker, sticking with the scratch partition conventions.

scratch.3Then it was once again a matter of editing the Advanced Settings for the hosts, and pointing the scratch location to the VVol datastore and subsequent sub-folders, via the setting ScratchConfig.ConfiguredScratchLocation, as shown here:

scratch.1The next step, as pointed out in the scratch config window above, is to reboot the host in order for this change take effect. Unfortunately, at this point the scratch partition reverted back to the original location and did not pick up the VVol datastore as the scratch location. So why was that? On further investigation, the logs show the following (scroll right to see more):

syslog.log:2015-04-24T11:59:54Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 2 seconds
syslog.log:2015-04-24T11:59:56Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 4 seconds
syslog.log:2015-04-24T12:00:00Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 8 seconds
syslog.log:2015-04-24T12:00:08Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 16 seconds
syslog.log:2015-04-24T12:00:24Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 32 seconds
syslog.log:2015-04-24T12:00:56Z jumpstart: mount point '/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored, waiting 64 seconds
syslog.log:2015-04-24T12:02:00Z jumpstart: mount point ‘/vmfs/volumes/vvol:b66d7f4a83854914-8d72065ca1c700b6/rfc4122.50264a8b-f396-42d7-a5f5-bf8c06c7646a/h11/.locker' not restored before timeout, giving up

So it would appear that the VVol datastore is not available when we wish to use it for scratch. All the services needed to mount a Config-VVol (such as the VVol service itself, osfsd, etc) are not configured early enough in the boot process to use as a scratch partition.

Conclusion

  • Syslog redirecting logs to a VVol datastore – works
  • Scratch redirected to a Vol datastore – doesn’t work

Hope this helps to answer the question. We are actively investigating what needs to be done to allow a VVol datastore to be used as a scratch partition by ESXi hosts.

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