On 10/02/2013 08:13 PM, Matthew Seaman wrote:
On 02/10/2013 16:34, Nikos Vassiliadis wrote:
Is there a way to know if a zfs pool had an unclean shutdown?
An attribute or maybe something during mount time similar to what ufs
does (WARNING: / was not properly dismounted)?
Other than looking at the system logs for evidence of an abnormal
shutdown, no. (Absence of anything in the logs is pretty good evidence
for the system falling over pretty hard... Usually something to do with
the power being turned off.)
However, due to the design of ZFS unclean shutdowns like this are
nowhere near as problematic as on UFS. Basically, you're guaranteed
that what is written on disk is always consistent. You might lose a few
transactions -- essentially the last few seconds of file system activity
-- but that doesn't usually make a great deal of difference after the
system reboots again. Oh, yeah -- absolutely no time will be needed to
be spent cleaning and repairing filesystems: with ZFS, reboot after
crash is as fast as a normal reboot.
Thanks Matthew, I realized I should have used a more appropriate
subject. I'll explain what my actual goal is:)
I am after a really specific use-case and the last minute transactions
are important. Using a zpool over geli over a zvol. I'd like to know if
during shutdown the kernel flushes all zfs files caches in order so
these last minutes transactions won't be lost. The unmounting order is
far from obvious (zfs over geli over zfs) and i wonder if such a scheme
will succeed. I can't afford losing the last transactions of my home dir
every time i shutdown my laptop;)
The obvious solution is to create two slices and dedicate a slice to
geli. Like this:
mypool lives on slice1
myencpool lives on slice2.eli
I am after this:
mypool lives on slice1
myencpool lives on /dev/zvol/mypool/avolume.eli
The second scheme will allow me to have an encypted home and not to
pre-allocate space. A quick test showed that it might work... On the
other hand conceptually seems like a very bad idea haha.
I think I've heard people doing this zfs over geli over zfs before...
Thanks for any thoughts, Nikos
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