Date: Fri, 04 Oct 2013 19:35:12 +0300 From: Volodymyr Kostyrko <c.kworr@gmail.com> To: Beeblebrox <zaphod@berentweb.com>, freebsd-fs@freebsd.org Subject: Re: Questions re swap-on-zfs Message-ID: <524EEE40.5060208@gmail.com> In-Reply-To: <1380880223590-5848720.post@n5.nabble.com> References: <1380880223590-5848720.post@n5.nabble.com>
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04.10.2013 12:50, 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. Yes. > 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 Nope. > 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? There's no need for SWAP to go through any caches or ZIL. > 4. Any other ideas to speed-up swap performance on tank0/swap? In fact I even tried this: * primarycache=metadata (that's would speed up finding blocks without caching them; * logbias=throughput (don't use ZIL); * sync=disabled (write data fast and right now); * checksum=off (if it's gone it's gone, period). The machine still hangs from time to time so I think you wouldn't be lucky too. PS: compression=lz4 makes this host survive longer but this can be just my imagination... -- Sphinx of black quartz, judge my vow.
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