Bit of a digression from my usual fare, but I thought I’d briefly share this as it was a slightly strange problem, and one that had me in a flap for a few minutes 🙂 I was booting a XenApp server from a shared Provisioning Services 5.1 disk image in Standard (read-only) mode a few days back and I noticed that on my Start Menu was a whole list of programs I’d just used before the restart. Now that shouldn’t have happened….and a quick look at the PVS notification area icon confirmed that indeed the disk was in Private (writable) mode. Cue me moving straight to the console – where this disk was listed as being in Standard mode. Yeah, what?
To make matters worse the server had started up in an OU where software was deployed via startup scripts (I know, horrible) so if the disk image really was in Private mode I’d just baked a whole host of apps (and static routes as well – ugh!) into an image that was intended for use by a whole slew of different customers. Why on earth was there a discrepancy between what the server using the image reported, and what the console thought was going on? Making me even more confused was the fact that another server was using the same image and had it showing correctly in Standard mode.
Naturally my next move was to have a look at the vDisk files on the stores in the PVS servers. And this is where I found out that these vDisks were being replicated by DFS – but someone had gone and helpfully turned the replication off. I don’t know a lot about PVS (yet – Mr Webster is constantly feeding me new titbits about it), but the timestamps of the image files were different on one PVS server to the other, and this is what made me go and check the DFS settings (which to be fair, you wouldn’t expect to be disabled). I don’t yet know how PVS replicates information like the startup mode, but it seemed to me that this was what had made one server think it had Write access to the vDisk. Once I assigned the PVS image to the server with the latest timestamp, rather than using the load-balanced pair, the image booted up in Standard mode on all systems as I would have expected.
So, if you see a discrepancy like this, take a look at the timestamps on the actual vDisk files. If there’s a big difference, you may have an issue with your replication.
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