Date: Tue, 9 Jul 2002 12:08:25 +1000 From: "Chris Knight" <chris@aims.com.au> To: <silby@silby.com> Cc: <hackers@FreeBSD.ORG> Subject: RE: offtopic: low level format of IDE drive. Message-ID: <004601c226ed$838bff50$020aa8c0@aims.private> In-Reply-To: <20020708195133.K19349-100000@patrocles.silby.com>
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Howdy, > -----Original Message----- > From: owner-freebsd-hackers@FreeBSD.ORG > [mailto:owner-freebsd-hackers@FreeBSD.ORG]On Behalf Of Mike Silbersack > Sent: Tuesday, 9 July 2002 10:53 > To: Peter Wemm > Cc: Julian Elischer; John Nielsen; hackers@FreeBSD.ORG > Subject: Re: offtopic: low level format of IDE drive. > > [snip] > > So, this basically means that even a journalling filesystem wouldn't > be much safer... how about battery backed up controllers - would those > provide protection? (I suspect not, but maybe they're more > sophisticated than I thought.) > That's right - a journalled filesystem doesn't help. Nor does battery backed up controllers. If the drive has come back and told the controller that it has written the data, then the controller - battery backed up or not - will mark those sectors as written. If it's a caching controller, then the cache entries for those sectors will be returned to the free list pool. The only way a journalled filesystem would help is if during replay, it checked that all the sectors matched prior to the checkpoint; ie write out all the sectors after the last checkpoint, then check sectors prior to the last checkpoint. That way, the journalled filesystem would know that the data had been written correctly. Does anyone have a detailed list of which SCSI drives do track writes rather than sector writes? Regards, Chris Knight Systems Administrator AIMS Independent Computer Professionals Tel: +61 3 6334 6664 Fax: +61 3 6331 7032 Mob: +61 419 528 795 Web: http://www.aims.com.au To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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