Date: Thu, 27 Mar 2014 21:20:11 +0100 From: Joar Jegleim <joar.jegleim@gmail.com> To: Johan Hendriks <joh.hendriks@gmail.com> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: zfs l2arc warmup Message-ID: <CAFfb-hoJCKV9D3DStVcZsBuZJLuUp8=pwFio6i2t3nyjoaOJHg@mail.gmail.com> In-Reply-To: <5333FB8F.7010500@gmail.com> References: <CAFfb-hpi20062%2BHCrSVhey1hVk9TAcOZAWgHSAP93RSov3sx4A@mail.gmail.com> <5333FB8F.7010500@gmail.com>
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thnx ! Read the first links many times before, but the second one was new to me and great reading ! On 27 March 2014 11:21, Johan Hendriks <joh.hendriks@gmail.com> wrote: > Joar Jegleim schreef: > >> Hi list ! >> >> I struggling to get a clear understanding of how the l2arc get warm ( >> zfs). >> It's a FreeBSD 9.2-RELEASE server. >> >> From various forum I've come up with this which I have in my >> /boot/loader.conf >> # L2ARC tuning >> # Maximum number of bytes written to l2arc per feed >> # 8MB (actuall=vfs.zfs.l2arc_write_max*(1000 / vfs.zfs.l2arc_feed_min_ms)) >> # so 8MB every 200ms = 40MB/s >> vfs.zfs.l2arc_write_max=8388608 >> # Mostly only relevant at the first few hours after boot >> # write_boost, speed to fill l2arc until it is filled (after boot) >> # 70MB, same rule applys, multiply by 5 = 350MB/s >> vfs.zfs.l2arc_write_boost=73400320 >> # Not sure >> vfs.zfs.l2arc_headroom=2 >> # l2arc feeding period >> vfs.zfs.l2arc_feed_secs=1 >> # minimum l2arc feeding period >> vfs.zfs.l2arc_feed_min_ms=200 >> # control whether streaming data is cached or not >> vfs.zfs.l2arc_noprefetch=1 >> # control whether feed_min_ms is used or not >> vfs.zfs.l2arc_feed_again=1 >> # no read and write at the same time >> vfs.zfs.l2arc_norw=1 >> >> But what I really wonder is how does the l2arc get warmed up ? >> I'm thinking of 2 scenarios: >> >> a.: when arc is full, stuff that evict from arc is put over in l2arc, >> that means that files in the fs that are never accessed will never end >> up in l2arc, right ? >> >> b.: zfs run through fs in the background and fill up the l2arc for any >> file, regardless if it has been accessed or not ( this is the >> 'feature' I'd like ) >> >> I suspect scenario a is what really happens, and if so, how does >> people warmup the l2arc manually (?) >> I figured that if I rsync everything from the pool I want to be >> cache'ed, it will fill up the l2arc for me, which I'm doing right now. >> But it takes 3-4 days to rsync the whole pool . >> >> Is this how 'you' do it to warmup the l2arc, or am I missing something ? >> >> The thing is with this particular pool is that it serves somewhere >> between 20 -> 30 million jpegs for a website. The front page of the >> site will for every reload present a mosaic of about 36 jpegs, and the >> jpegs are completely randomly fetched from the pool. >> I don't know what jpegs will be fetched at any given time, so I'm >> installing about 2TB of l2arc ( the pool is about 1.6TB today) and I >> want the whole pool to be available from the l2arc . >> >> >> Any input on my 'rsync solution' to warmup the l2arc is much appreciated >> :) >> >> > A nice blog about the L2ARC > > https://blogs.oracle.com/brendan/entry/test > > https://blogs.oracle.com/brendan/entry/l2arc_screenshots > > regards > Johan -- ---------------------- Joar Jegleim Homepage: http://cosmicb.no Linkedin: http://no.linkedin.com/in/joarjegleim fb: http://www.facebook.com/joar.jegleim AKA: CosmicB @Freenode ----------------------
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