Hey, I had many external hard drive crash (savage unplug, power off, pc forced restart). The server on the virtual machine was never hurt, nor the data.
Cheers, Rémi-C 2014-09-12 15:34 GMT+02:00 George Neuner <gneun...@comcast.net>: > Hi Craig, > > On Fri, 12 Sep 2014 11:33:55 +0800, Craig Ringer > <cr...@2ndquadrant.com> wrote: > > >On 09/11/2014 03:16 PM, George Neuner wrote: > >> > >> If the driver permits it and you [or your users] can be trusted to > >> perform a safe unmount via the OS *before* disconnecting the device, > >> then you can enable write caching for the device using the device > >> manager. [Note that the device must be connected for it to be visible > >> in the device manager.] > > > >It shouldn't be living dangerously, actually. > > > >While I haven't tested it myself, writeback caching on the external > >drive should be safe so long as it continues to honour explicit disk > >flush requests. > > > >That's why we have the WAL and do periodic checkpoints. If you yank the > >drive mid-write you'll lose uncommitted transactions and might have > >slower startup next time around, but it should otherwise not be overly > >problematic. > > For the most part you're correct, but recall that WAL itself can be > made asynchronous [see fsync() and synchronous_commit() settings] and > the periodic OS sync also may be disabled - which doesn't affect WAL > handling but may(?) affect the background writer. > > Even having synchronous WAL the most recent transactions can be lost > if the log device fails *during* a write. That's why, if we use > external devices at all, we tend to use closely coupled devices - disk > array, wired SAN, etc. - that aren't very likely to be physically > disconnected. And uninterruptible power all around 8-) > > A portable device can be reasonably safe if treated properly, but it > never will be quite as safe as an internal device. > > George > > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
