Date: Wed, 10 Jun 2009 10:55:15 -0500 From: Chris Dillon <cdillon@wolves.k12.mo.us> To: Dmitry Morozovsky <marck@rinet.ru> Cc: freebsd-hackers@freebsd.org, freebsd-current@freebsd.org Subject: Re: sysinstall, GJOURNAL and ZFS Message-ID: <20090610105515.138862z6opgohgtf@www.wolves.k12.mo.us> In-Reply-To: <alpine.BSF.2.00.0906101428591.49870@woozle.rinet.ru> References: <alpine.BSF.2.00.0906091632430.6551@wojtek.tensor.gdynia.pl> <cf9b1ee00906090757v7d589dfch978076a97be724a9@mail.gmail.com> <20090609172142.GA92146@ebi.local> <20090609.195750.41709103.sthaug@nethelp.no> <86hbyowgj6.fsf@ds4.des.no> <alpine.BSF.2.00.0906101428591.49870@woozle.rinet.ru>
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Quoting Dmitry Morozovsky <marck@rinet.ru>: > Well, I can see at least one rather big problem with bgfsck (or with > snapshots to be more precise): inappropriate time of file system > lock on snapshot creation. On not-too-big 300G ufs2 not-too-heavy > loaded snapshot creation time is 20+ minutes, and 5+ from that file > system blocked even on reads. This looks unacceptable for me for > any real use. The snapshot time depends heavily on the I/O throughput of your disk subsystem. On a several year old system with 5 x 72GB 15KRPM U320 SCSI drives in a RAID5 array, a fairly well loaded 260GB filesystem (90GB used, 354K out of 8M inodes used, and several hundred MB to a GB of changes per day) completes a snapshot in exactly 2 minutes. 2 minutes is still too long to be blocking I/O in the middle of the day when it is being actively used, so I just take 1 snapshot per day while it is idle. I would love to put ZFS on this system so that I could have finer grained snapshots, but I need user quota support which our ZFS currently lacks. -- Chris Dillon - NetEng/SysAdm Reeds Spring R-IV School District Technology Department 175 Elementary Rd. Reeds Spring, MO 65737 Voice: 417-272-8266 Fax: 417-272-0015
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