Swap on ZFS

Anselm Strauss amsibamsi at gmail.com
Sat Oct 2 09:30:47 UTC 2010


I have a virtual server with only 512 MB of memory but still want to run
ZFS on it. When there is IO load and only few memory left it
occasionally happens that the server freezes, network ping will still
work. As far as I know there was the problem that an IO request on ZFS
first needs to allocate some memory before it can be run. So in the case
where no memory is left and some swap must be used which lies also on
ZFS, it would still first need some free memory for the request. This
basically results in a deadlock and the system freezes.

Would this not happen every time when the system is out of memory and
swap must be used? So it basically makes swap on ZFS useless.

Has there been any fix or workaround for this? I guess it does not help
when I use a swap file on ZFS instead of a separate zvol.

Appreciating any ideas

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