Date: Thu, 8 Jan 2009 00:45:47 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/cam/scsi scsi_cd.c Message-ID: <200901080045.n080jrbD099578@repoman.freebsd.org>
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imp 2009-01-08 00:45:47 UTC
FreeBSD src repository
Modified files:
sys/cam/scsi scsi_cd.c
Log:
SVN rev 186882 on 2009-01-08 00:45:47Z by imp
Make it possible to override the number of retries for the CD media.
When trying to read scratched or damaged CDs and DVDs, the default
mechanism is sub-optimal. Programs like ddrescue do much better if
you turn off retries entirely, since their algorithms are designed
scan big areas fast, then winnow the areas down. Turning off retries
speeds these programs up by as much as 20x, since the drive is able to
'stream past' many small errors...
The sysctl/tunable kern.cam.cd.retry_count controls this. That
defaults to '4' (for a total of 5 attempts). Setting to 0 turns off
all retry attempts.
Reviewed by: scottl@
Revision Changes Path
1.104 +8 -1 src/sys/cam/scsi/scsi_cd.c
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