Date: Thu, 20 May 2004 16:15:51 -0400 From: Mikhail Teterin <mi+mx@aldan.algebra.com> To: Steve Byan <smb@egenera.com> Cc: Julian Elischer <julian@elischer.org> Subject: Re: QMail and SoftUpdates Message-ID: <200405201615.51539@misha-mx.virtual-estates.net> In-Reply-To: <D4BFC35E-AA97-11D8-B0BF-000A957CD5B0@egenera.com> References: <20040517174836.GA983@frontfree.net> <40A974DA.30704@comcast.net> <D4BFC35E-AA97-11D8-B0BF-000A957CD5B0@egenera.com>
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=> Even if the OS crashes, as long as power is supplied to the drive, => its firmware should finish writing the data from its cache to the => disk media, no? And therefore, as long as one has a stable power => source, e.g. running off a UPS, there really isn't any great risk => from on-drive write caches, is there? = =No. Unlike SCSI disks, ATA disks will toss their write-cache on a =reset. When the system crashes and the BIOS starts rebooting, guess =what it issues to the ATA disks? Yep, a reset. So with ATA write-cache =enabled, your filesystem is likely to be toast after a crash, as well =as after a power failure. Is not this only of concern if the power is restored and the BIOS resets the disks _before_ they flush their write caches? I'd expect them to do that (the flushing) within seconds anyway, no? -mi
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