Date: Mon, 4 Mar 2002 22:27:55 -0800 (PST) From: Tom Samplonius <tom@sdf.com> To: Patrick Thomas <root@utility.clubscholarship.com> Cc: freebsd-scsi@freebsd.org Subject: Re: Dell PERC scrub / scrubbing question Message-ID: <Pine.BSF.4.05.10203042220520.9032-100000@misery.sdf.com> In-Reply-To: <20020304220244.T84242-100000@utility.clubscholarship.com>
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On Mon, 4 Mar 2002, Patrick Thomas wrote: > When I created my mirrors originally with my Dell PERC 2 controller, they > immediately started scrubbing. The BIOS told me not to use them until > they were done scrubbing. Fair enough. Depends on what they mean by scrubbing. It usually takes a long time to initialize a RAID5 volume, because the parity is created for the first time. Scrubbing usually refers to reading all blocks, and verifying that the parity matches. This is used to detect bad blocks on a disk. Not all RAID controllers even do this. Scrubbing is important for RAID5, because if a disk develops a bad area where some infrequently accessed files are stored, you might be in for an unpleasent surprise if you try to read them when the array is running degraded. On systems that I've seen that do scrubbing, they always implement it as a low-priority background task as to not to impair normal volume activity. It might be possible to configure the scrubbing priority, as well as the scrubbing schedule. Tom To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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