Date: Fri, 25 Jan 2008 13:18:22 -0800 From: Chuck Swiger <cswiger@mac.com> To: Thomas Hurst <tom.hurst@clara.net> Cc: Joe Peterson <joe@skyrush.com>, freebsd-stable@freebsd.org Subject: Re: "ad0: TIMEOUT - WRITE_DMA" type errors with 7.0-RC1 Message-ID: <5D6C699B-A8D2-4ACD-A9F6-5CB263A88B42@mac.com> In-Reply-To: <20080125210527.GA40754@voi.aagh.net> References: <479A0731.6020405@skyrush.com> <20080125162940.GA38494@eos.sc1.parodius.com> <479A3764.6050800@skyrush.com> <3803988D-8D18-4E89-92EA-19BF62FD2395@mac.com> <20080125210527.GA40754@voi.aagh.net>
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On Jan 25, 2008, at 1:05 PM, Thomas Hurst wrote: >> These numbers are quite worrysome-- they should be zero or nearly >> so in a >> healthy drive. > > No, these are perfectly reasonable for a Seagate. I have about 12 > 7200.X's and all show the same sort of behavior. If they're nearly > zero > it's probably a sign your manufacturer isn't actually counting them > (marketroids hate accurate SMART readings). > > Try graphing them as counters; with an idle disk you'll see periodic > sawtooth patterns as the heads crawl from one side of the disk to the > other. SMART attributes which end with _Ct or _Count are supposed to increment with every event; things which end with _Rate (ie, Raw_Read_Error_Rate, Seek_Error_Rate) are supposed to indicate the frequency of such errors over time. It would be reasonable for Hardware_ECC_Recovered to keep the incremental count, but not the other two. I agree that minor periodic errors happen over time and are not a great concern, but a happy drive will show zero reallocated sectors, or perhaps a few over the span of a year or two, and will have a ECC recovered or UDMA_CRC count which is much smaller than was reported by Joe. YMMV, of course... -- -Chuck
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