Date: Fri, 04 Oct 2013 12:42:29 +0200 From: Johan Hendriks <joh.hendriks@gmail.com> To: Beeblebrox <zaphod@berentweb.com> Cc: freebsd-fs@freebsd.org Subject: Re: Questions re swap-on-zfs Message-ID: <524E9B95.9010307@gmail.com> In-Reply-To: <1380880223590-5848720.post@n5.nabble.com> References: <1380880223590-5848720.post@n5.nabble.com>
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Beeblebrox wrote: > I have 2 swap devices on my system. #1-tank0/swap on ZFS, #2-/dev/ada0p1 on > SSD 1GB. I have some questions for swap-on-zfs: > > 1. I had read in the past that swap-on-zfs can cause instability if memory > gets used to full capacity. Is this still the case, or has that issue been > corrected? The reason I created swap-#2 is precisely for this purpose; a > small backup resource. > > 2. If the problem still persists, I would like to tweak the setup so that > swap-#2 is only used as last resort. I tried setting the priority (pri) in > fstab, but it does not seem to work - how can this be done? > /dev/ada0p1 none swap sw,pri=0 0 0 > tank0/swap none zfs sw,pri=9 0 0 > > 3. Is it necessary for the data on swap to go through the Intent Log? I have > a separate ZIL device for tank0 pool. What risk is there if I disable the > log for the swap dataset? Is this done by modifying the "primarycache" > parameter for dataset? > > 4. Any other ideas to speed-up swap performance on tank0/swap? > > Regards. > I have one machine that has swap on ZFS. This is the only machine that hangs completely when a swap starvation occurs. It happens regualy because it is an old machine with only 2GB of RAM. That machine is running a version of FreeBSD 9.1 stable from april i guess. It is not an heavy duty server just an offsite backup system, so I can live with it. All other machines tho heavier on RAM have no problems even when a swap starvation occurs. I will not use swap on ZFS anymore. regards Johan Hendriks
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