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Re: [smartmontools-support] Which attributes can estimate number of bad blocks?
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From: <ro...@sp...> - 2016-08-01 19:43:14
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If you ASSUME that pending sectors are bad, then yes, add reallocated and pending. Generally though, if there are only 1 or 2, they are not bad. I wouldn't add 187 and 198, as they can indicate unrelated problems. > Thank you for explaining that a current pending sector isn't always going > to be reallocated by the drive. I don't see how soft error differs from > bad sector though. Also a medium error is a bad sector but the drive > thinks a write fixed the sector. > > However, you didn't address my question. I'm trying to estimate the > number of sectors already found to be bad. I was adding the raw value of > attributes 5 and 197 to get a quick estimate. My question is whether to > add raw values of attributes 187 and 198 as well, or are these redundant > (already included in) attributes 5 and 197? > > If the estimated number is below some psychological limit (not set by me) > then I proceed to more intensive testing. If the estimate is over the > psychological limit then the drive can be assigned to scrap without > needing any further testing. So I'm trying to make a reasonable estimate. > > > ----- Original Message ----- >>From: "ro...@sp..." <ro...@sp...> >>To: Norman Diamond <n0d...@ya...> >>Cc: "sma...@li..." >> <sma...@li...> >>Date: 2016/7/28, Thu 23:34 >>Subject: Re: [smartmontools-support] Which attributes can estimate >> number of bad blocks? >> >>Current Pending Sector can indicate one of 3 things [on platter drives]: >> >>* A bad sector that hasn't been reallocated yet, i.e. written to (a hard >>error). >>* A soft error. One or 2 sectors might indicate this problem. Every drive >>I've seen so far with 8+ turned out to be a bad drive. >>* The most insidious of all, a medium error. The sector can't hold it's >>charge, for long. You can write to it then immediately read from it OK, >>but usually in less than an hour, it goes corrupt again. You'll see that >>in the same sector(s) keeps failing. This is a drive you should trash. >> >>It sounds like you have a drive with medium error(s). >> >>As for trashing a drive, it varies depending on who you ask, but at 5+ >>(raw value) reallocated, I trash. At 8+ Pending, I trash. >> >>In regards to 187 and 197, I will retire a drive with any raw value more >>than 0. But this is based more on Backblaze's published results than my >>own observations. Usually I don't see those, or the drive is already >>failing based on Reallocated and Pending. >> >>> To get a quick estimate of the number of bad blocks that have already >>> been >>> detected, I add the raw values of attributes 5 (Reallocated_Sector_Ct) >>> and >>> 197 (Current_Pending_Sector). >>> >>> Should I also add the raw values of attributes 187 (Reported_Uncorrect) >>> and 198 (Offline_Uncorrectable)? Or are these redundant, already >>> included >>> in attributes 5 and 197? >>> >>> Are there others that I should add? >>> >>> Of course this estimate isn't as reliable as ... well actually, other >>> methods of testing aren't particularly reliable either[*]. Anyway the >>> reason for getting a quick estimate is that if we know quickly that a >>> drive belongs on the scrap heap, it saves time. >>> >>> [* I have a drive with particularly bad firmware. Reading the entire >>> drive causes Current_Pending_Sector to increase. Writing the bad >>> sectors >>> doesn't cause Reallocated_Sector_Ct to increase but does cause >>> Current_Pending_Sector to go down to 0. I guess the drive thinks that >>> a >>> write operation fixed the sector so the sector doesn't need >>> reallocation, >>> but the next attempt to read shows that the sector didn't get fixed. >>> If >>> the drive were in warranty, I might not have it any more :-) ] >>> >>> >>> ------------------------------------------------------------------------------ >>> _______________________________________________ >>> Smartmontools-support mailing list >>> Sma...@li... >>> https://lists.sourceforge.net/lists/listinfo/smartmontools-support >>> >> >> >> >> >> > > ------------------------------------------------------------------------------ > _______________________________________________ > Smartmontools-support mailing list > Sma...@li... > https://lists.sourceforge.net/lists/listinfo/smartmontools-support > |
