Date: Wed, 13 May 2009 07:51:04 -0700 From: Kip Macy <kmacy@freebsd.org> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: UFS2 and SSDs Message-ID: <3c1674c90905130751s60757be2t8039965b71c75467@mail.gmail.com> In-Reply-To: <guelk2$jab$1@ger.gmane.org> References: <49FC1BD0.4030306@T-Online.de> <guecop$jtd$1@ger.gmane.org> <3c1674c90905130529r70589318tf57198d24cf2bd57@mail.gmail.com> <20090513135335.GA42884@voi.aagh.net> <guelk2$jab$1@ger.gmane.org>
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On Wed, May 13, 2009 at 7:31 AM, Ivan Voras <ivoras@freebsd.org> wrote: > Thomas Hurst wrote: >> * Kip Macy (kmacy@freebsd.org) wrote: >> >>> I accidentally bought a camera-grade SSD. Random write performance >>> with UFS made it unusable. I ended up converting /usr to ZFS - since >>> which time I've been very happy with performance. >> >> Did you try gjournal on it? =A0SSD's should do better with sequential >> journal writes. > > My guess is that it won't matter - the issue is "small writes" not > "sequential writes". Gjournal will issue writes as it receives them - if > it receives a bunch of small ones, it will pass them on in the same > form, only sequential (the drive will still see a bunch of small > writes). This works well for mechanical drives because of rotational > properties but does nothing to SSDs. > > ZFS OTOH does a great deal of buffering. The benefits come from write-allocate - writes always end up being some multiple of erase blocks. With FFS the drive constantly has to GC partial blocks. -Kip --=20 When bad men combine, the good must associate; else they will fall one by one, an unpitied sacrifice in a contemptible struggle. Edmund Burke
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