Date: Fri, 4 Oct 2013 14:27:16 -0400 From: Zaphod Beeblebrox <zbeeble@gmail.com> To: Volodymyr Kostyrko <c.kworr@gmail.com> Cc: freebsd-fs <freebsd-fs@freebsd.org>, Beeblebrox <zaphod@berentweb.com> Subject: Re: Questions re swap-on-zfs Message-ID: <CACpH0McMfQ3r-n-ijL6Aoum=QoMY_FczBzu3vt%2BcYwCJkCNOzw@mail.gmail.com> In-Reply-To: <524EEE40.5060208@gmail.com> References: <1380880223590-5848720.post@n5.nabble.com> <524EEE40.5060208@gmail.com>
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While I remain convinced that swap on ZFS is bad, it also precludes getting a dump, so I configure my ZFS systems with a partition for swap and a partition for ZFS on each drive. This has the additional bonus of making swap effectively faster on a 2 drive system (2 swap partitions). On Fri, Oct 4, 2013 at 12:35 PM, Volodymyr Kostyrko <c.kworr@gmail.com>wrote: > 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. > > ______________________________**_________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/**mailman/listinfo/freebsd-fs<http://lists.freebsd.org/mailman/listinfo/freebsd-fs>; > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@**freebsd.org<freebsd-fs-unsubscribe@freebsd.org> > " >
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