Date: Wed, 9 Jul 2014 08:21:18 +0100 From: krad <kraduk@gmail.com> To: kpneal@pobox.com Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Re: Using 2 SSD's to create a SLOG Message-ID: <CALfReyeDpW-ELW9zmVFue%2Bw6HrO-iepwUcf2chwLHofFfshrcg@mail.gmail.com> In-Reply-To: <20140708025106.GA85067@neutralgood.org> References: <CAP1HOmRe5hEts6qA=0ZiNbMt%2B%2BDoyJO1f0fs=Wnx4ceC%2BygWeg@mail.gmail.com> <20140708025106.GA85067@neutralgood.org>
next in thread | previous in thread | raw e-mail | index | archive | help
An NFS server is a common task that generates lots of synchronous writes On 8 July 2014 03:51, <kpneal@pobox.com> wrote: > On Mon, Jul 07, 2014 at 06:06:43PM -0700, javocado wrote: > > I am interested in adding an SSD "SLOG" to my ZFS system so as to > > (dramatically) speed up writes on this system. > > > > My question is if ZFS will, itself, internally, mirror two SSDs that are > > used as a SLOG ? > > > > What I mean is, if ZFS is already smart enough to create a zpool mirror > > (or, on my case, a zpool raidz3) then perhaps ZFS is also smart enough to > > mirror the SLOG to two individual SSDs ? > > > > I am hoping to dumbly plug two SSDs onto motherboard SATA ports and just > > hand them over, raw, to ZFS. > > From the zpool man page: > > Example 12 Creating a ZFS Pool with Mirrored Separate Intent Logs > > The following command creates a ZFS storage pool consisting of > two, > two-way mirrors and mirrored log devices: > > # zpool create pool mirror c0d0 c1d0 mirror c2d0 c3d0 log mirror \ > c4d0 c5d0 > > You should be able to use that example to make the 'zpool add' command to > add the mirrored log to an existing pool. > > But know that the SLOG only helps writes that are synchronous. This is in > many workloads a small fraction of the total writes. For other workloads > it is a large portion of the writes. > > Do you know for certain that you need a SLOG? > -- > Kevin P. Neal http://www.pobox.com/~kpn/ > On the community of supercomputer fans: > "But what we lack in size we make up for in eccentricity." > from Steve Gombosi, comp.sys.super, 31 Jul 2000 11:22:43 -0600 > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CALfReyeDpW-ELW9zmVFue%2Bw6HrO-iepwUcf2chwLHofFfshrcg>