Paul Kraus via illumos-zfs
2014-08-18 16:58:16 UTC
I figure I have a much better chance of a definitive answer here than on the freebsd-questions list …
I am running both FreeBSD 9 and 10.
What is the state of the ZFS ARC free code for each? By this I mean the code that frees memory from the ARC as memory pressure from the OS and other applications grows. I have heard rumor (maybe FUD) that this code in FreeBSD is not terrible good and that there can be issues. I have lots of experience with this code under Solaris 10 and it seemed to just work and *not* get in the way of other things needing RAM.
Part of the reason I ask is that I have one server (running 9.1, have not been able to upgrade) that has run into an issue with a swap volume on a zvol (swapd hangs in what looks like a race state). I have found a couple references to issues putting swap on zvol on FreeBSD, so my short term fix (we are getting more hardware which will permit me to move VMs and upgrade this server) is to run without a swap device. I know the many limitations of this configuration and they are acceptable in this case. I am (obviously) trying to manage my RAM very carefully and *if* I can count on the ZFS ARC code giving back RAM reliably I can configure a larger ARC MAX than otherwise.
In the more general (and FreeBSD 10) case, this will determine how carefully I need to manage RAM moving forward on the FreeBSD systems (the future architecture will be a mix of SmartOS and FreeBSD).
Thanks.
--
Paul Kraus
***@kraus-haus.org
I am running both FreeBSD 9 and 10.
What is the state of the ZFS ARC free code for each? By this I mean the code that frees memory from the ARC as memory pressure from the OS and other applications grows. I have heard rumor (maybe FUD) that this code in FreeBSD is not terrible good and that there can be issues. I have lots of experience with this code under Solaris 10 and it seemed to just work and *not* get in the way of other things needing RAM.
Part of the reason I ask is that I have one server (running 9.1, have not been able to upgrade) that has run into an issue with a swap volume on a zvol (swapd hangs in what looks like a race state). I have found a couple references to issues putting swap on zvol on FreeBSD, so my short term fix (we are getting more hardware which will permit me to move VMs and upgrade this server) is to run without a swap device. I know the many limitations of this configuration and they are acceptable in this case. I am (obviously) trying to manage my RAM very carefully and *if* I can count on the ZFS ARC code giving back RAM reliably I can configure a larger ARC MAX than otherwise.
In the more general (and FreeBSD 10) case, this will determine how carefully I need to manage RAM moving forward on the FreeBSD systems (the future architecture will be a mix of SmartOS and FreeBSD).
Thanks.
--
Paul Kraus
***@kraus-haus.org