Date: Mon, 22 Jun 2009 01:36:26 +0300 From: Dan Naumov <dan.naumov@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: ufs2 / softupdates / ZFS / disk write cache Message-ID: <cf9b1ee00906211536i37973627ub86948aea63b4156@mail.gmail.com> In-Reply-To: <cf9b1ee00906211534i76fc8fb4r29b3469af8a2fd7c@mail.gmail.com> References: <570433.20373.qm@web37308.mail.mud.yahoo.com> <4A3E9D81.1060406@modulus.org> <cf9b1ee00906211534i76fc8fb4r29b3469af8a2fd7c@mail.gmail.com>
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---------- Forwarded message ---------- From: Dan Naumov <dan.naumov@gmail.com> Date: Mon, Jun 22, 2009 at 1:34 AM Subject: Re: ufs2 / softupdates / ZFS / disk write cache To: Andrew Snow <andrew@modulus.org> On Sun, Jun 21, 2009 at 11:52 PM, Andrew Snow <andrew@modulus.org> wrote: > > =8Aimun Mikecin wrote: >> >> 21. lip. 2009., u 13:41, Andrew Snow <andrew@modulus.org> napisao: >>> >>> Folks who need to maximize safety and can't afford the performance =A0h= it of no write cache need to do what they always have had to do in =A0the p= ast - buy a controller card with battery-backed cached. >> >> Or: >> B) use SCSI instead of ATA disks >> C) use UFS+gjournal instead of UFS+SU >> D) use ZFS instead of UFS+SU > > > All of these solutions still involve disabling of write cache, with a per= formance hit of varying degrees. (I have tried all of those except gjournal= !) Why would using UFS+gjournal, ZFS or SCSI still involve disabling write cache? Disabling write cache is only suggested for systems using UFS + SU on ATA/PATA disks. This in turn actually raises a new point: Why is UFS + SU still the default option provided by the sysinstall installation process? A simple truth is that most FreeBSD users on a modern system are going to be using SATA disks. Another simple truth is that most new users are going to go with what the default installation process suggests and as shown by the benchmark results a few posts back, noone is going to be disabling the write cache unless they are completely out of their mind (who on earth is going to accept 2-4 MB/s write speeds from a modern disk in 2009?). - Dan Naumov
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