Date: Fri, 31 Jan 2003 16:01:13 -0500 From: Steve Byan <stephen_byan@maxtor.com> To: David Schultz <dschultz@uclink.Berkeley.EDU> Cc: phk@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG, tech-kern@netbsd.org Subject: Re: DEV_B_SIZE Message-ID: <21B8D16C-355F-11D7-B26B-00306548867E@maxtor.com> In-Reply-To: <20030131192452.GA15985@HAL9000.homeunix.com>
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On Friday, January 31, 2003, at 02:24 PM, David Schultz wrote: > If the disk corrupts a sector it was writing, that's already a > problem for us. =46rom the Maxtor Atlas 10K III Product Spec: Section 4.5.1 Power Sequencing You may apply the power in any order or manner, or open either the=20 power or power return line with no loss of data or damage to the disk drive.=20 However, data may be lost in the sector being written at the time of power loss.=20= The drive can withstand transient voltages of +10% to =96100% from nominal while powering up or down. > If the sector is 4K, that just makes it more of a > problem. With FFS and soft updates, we assume that the disk can > atomically write 512 bytes, and we ensure filesystem consistency > by establishing a safe partial ordering for metadata updates. We > expect that after a crash, either the old contents or the new > contents of the sector are there. I think we would need to > implement journalling to ensure integrity if hard drives were > likely to corrupt sectors on power failure. (How often do they do > this right now, and how often would they with 4K sectors?) If you are doing nothing but continuously writing, the active data area=20= covers more than 50% of the track, so you'd have more than a 0.5=20 probability of experiencing a corrupt sector. Derate this by your seek=20= duty-cycle and your write disk utilization to arrive at the final=20 probability. Regards, -Steve -------- Steve Byan <stephen_byan@maxtor.com> Design Engineer Maxtor Corp. MS 1-3/E23 333 South Street Shrewsbury, MA 01545 (508) 770-3414 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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