zfs and swap working?

[Ivan Voras]

On 08/06/2012 17:06, Volodymyr Kostyrko wrote:
> Hi all.
> 
> Didn't I miss anything? Someone has fixed swap to zfs vdevs?

> This is just after surviving one night trying to rebuild lang/pypy
> without enough memory. Everything works fine, swap data is also
> compressed and cached on cache device.

It has always worked for light, non-demanding loads.

As you've also described in your post, ZFS may need to do a lot of
operations between when it gets data and when it writes data to the
drives (you mention compression and caching, but there's also RAID,
checksumming, etc) and all these operations require ZFS to allocate
memory. If memory is really scarce, you can get the situation where the
system tries to free memory by swapping, only to have the swapper
require more memory to perform the operation.

Or at least this used to be the case. Quick Googling show that Solaris
has documented that swapping to ZVOLs should work - I wonder how they
get around these types of problems. It looks like they can also dump to
ZVOls (http://docs.oracle.com/cd/E19963-01/html/821-1448/ggrln.html).



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