[Users] Pstorage and read-only FS problem

Kirill Korotaev dev at parallels.com
Sat Jan 16 03:45:11 PST 2016


In situations like yours pstorage will keep running everything fine - and you won’t even need to stop containers/VMs on that node.
In other words - it will still use that node for reads (while it is able to serve the reads and doesn’t generate read errors), but won’t use for writes.
It will also start copying the data to other nodes in background to make sure redundancy level is satisfied.


On 16 Jan 2016, at 12:26, Corrado Fiore <lists at corradofiore.it> wrote:

Dear All,

we had recently experienced a filesystem corruption issue on a big-ish host where the HW RAID card suddenly started to behave erratically.

After a few minutes, the OS (OVZ kernel 2.6.32) put the /vz filesystem in read-only, which forced us to shut down the entire node, check the FS with the usual tools, etc. and ultimately lead to a significant downtime.

On that node we weren’t using pstorage - just a regular EXT4 file system on top of the RAID array… which brings us to my question for the pstorage experts on the list.

Let’s assume that instead of a regular EXT4 file system, we were using pstorage with 5 or more nodes and triple redundancy.

In a case where the entire FS of a pstorage chunk server suddenly becomes read-only, but the server itself is still on and responding to network probes, does the pstorage fencing mechanism automatically intervene to exclude that chunk server?

In simple terms, I am trying to find out whether in such a case pstorage (coupled with HA features of the commercial Virtuozzo) would have prevented downtime.  I suspect it would, just searching for some official confirmation from the experts.  :-)

Thanks a lot,
Corrado Fiore
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