Date: Sun, 16 Mar 2008 14:11:54 +0100 From: Arnaud Houdelette <arnaud.houdelette@tzim.net> To: freebsd-geom@freebsd.org Subject: Geom_Raid5 best practices ? Message-ID: <47DD1C9A.1020208@tzim.net>
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I use geom_raid5 for my home NAS for nearly 1 year. No problems so far (but just the fact I had to patch ata-disk.c to modify the IO timeout in order to be able to use ataidle). Since I updated to 7.0-RELEASE, I was wondering if I should use gjournal on the raid5 array. The array's purpose is to store music (2-10 MB) and video (300MB to 8GB) files. My system is as it follow : - USB key for base system (power/sound efficient) - 120 GB Pata disk for temporary downloads, /usr/src, ports and obj - 4x250 GB sata disks for mass storage (so 750GB usable space). I currently use plain UFS+SU on every FS, and daily snapshots on the raid5 one. GJournal should protect the raid5 UFS from destruction by bad power failures/kernel crashes, but with what performance impact ? Is the risk of complete FS crash really important with only SU ? (loss of data written at the time of the crash is no big deal, nor waiting for a fsck to complete, as long as I can recover most of the data previously stored) But as the gjournal first introduction showed a big performance drop on big files (they apparently have to be written twice), I was really wondering if I should use a journal on the file system ? If so, where should I put the journal on, and wich journal size should I use ? Any advice ?
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