Simultaneous read-only snapshot mount
Andriy Gapon
avg at FreeBSD.org
Mon Feb 13 16:45:26 UTC 2012
on 13/02/2012 17:55 Kevin Day said the following:
>
> It's now possible/somewhat common for the ability to have two systems can see
> the same disk(s) at the same time (through iSCSI or storage systems that
> support dual controllers, etc).
>
> Suppose system A has a filesystem mounted RW, and takes a snapshot. Can system
> B access that snapshot via a read only mount, while system A continues to
> read/write to that filesystem? Or more basically, is everything needed to read
> a snapshot stable/unchanging enough that a second system can read from it while
> the filesystem is still being updated?
Generally, no. The RO fs typically still caches a lot of information (metadata)
in RAM, the cached data may become stale and inconsistent.
--
Andriy Gapon
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