Date: Wed, 22 Jun 2011 06:51:53 +0200 From: Wiktor Niesiobedzki <bsd@vink.pl> To: Artem Belevich <art@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS L2ARC hit ratio Message-ID: <BANLkTikmtOwYYLjsQBMBND9L6YsLkD8jhg@mail.gmail.com> In-Reply-To: <BANLkTindsp-WqoTySZtym8LtX7DnMgjD-g@mail.gmail.com> References: <BANLkTinyveD7D=PYv3eqdxZb=KneKxg9Zg@mail.gmail.com> <BANLkTindsp-WqoTySZtym8LtX7DnMgjD-g@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
2011/6/22 Artem Belevich <art@freebsd.org>: > > L2ARC is filled with items evicted from ARC. The catch is that L2ARC > writes are intentionally throttled. When L2ARC is empty writes happen > at a higher rate, but it's still intentionally low so that > read-optimized cache device does not wear out too soon. The bottom > line is that not all the data spilled out of ARC ends up in L2ARC on > the first try. Re-run your experiment again and you would probably see > some improvement in L2ARC hit rates. I've run the experiment 3 times with no extent. Funny thing is: - in first run, I see a lot of write activity against cache device - in second run, I see no write activity against cache device, nor read activity So my guess is, that anyhow, ZFS cache layer knows, that this file is *there*, though it decides not to serve it from L2ARC... Cheers, Wiktor
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?BANLkTikmtOwYYLjsQBMBND9L6YsLkD8jhg>