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Author Topic: Reallocated sectors Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 12-30-2019 11:06 AM                     One of the server manufacturers will tell you that a hard disk is considered bad and should be replaced if a single reallocated sector is found. My understanding is that the whole point of reallocated sectors is to mark the sector as bad and not ever use it so the disk can continue to function normally. What are your thoughts on the subject? Should a disk be replaced if a single reallocated sector is found? If not, what is the acceptable limit? MODS: Please move to Digital forum. I didn't realize I posted this in FHF.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 12-30-2019 11:47 AM                     Besides SSDs, who mostly hide the "reallocated sector" thing, because the way a modern SSD is being written to is completely different than hard drives due to wear-levelling, you'll have a hard time finding disks without a single reallocated sector after a bit of use. The thing to monitor isn't so much the amount of reallocated sectors, because it also depends on the size of the drive, the thing to monitor is much more if this number is growing. If it is rapidly growing, you'll want to replace the drive asap.  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 12-30-2019 12:55 PM                     So if I notice a handful of reallocated sectors and the number never grows, I'm probably good, yeah?  |  IP: Logged Ed Gordon Film Handler Posts: 31 From: Mountlake Terrace, WA, USA Registered: May 2019 posted 12-30-2019 01:28 PM                     Ken, as Marcel said, if reallocated sector count is not rapidly increasing you should be fine. Another thing to keep in mind is that the reserved area designated for reallocation of bad sectors is defined by the disk manufacturer and does not dynamically increase in capacity. If you have the bad luck to fill the reserved area, you may loose data.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-30-2019 10:35 PM                     Generally, with HDDs...I'll allow under 10 Reallocated sectors, unless the drive is 5 years old or more...then I'm much more touchy. It is definitely the case that if you see the count growing in any short amount of time (days, weeks or eve a month)...change the drive. Drives are cheap, downtime isn't.  |  IP: Logged John Thomas Film Handler Posts: 75 From: Boston, MA Registered: Sep 2011 posted 12-31-2019 02:16 AM                     I always defer this sort of question to the Google whitepaper on HDD failure trends: https://research.google/pubs/pub32774/ quote: After their first reallocation, drives are over 14 times more likely to fail within 60 days than drives without reallocation counts, making the critical threshold for this parameter also one. Like Steve said: drives are cheap, downtime isn't.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-31-2019 05:59 AM                     I have not found the odd reallocation to be an indicator of pending failure. On the sites we support, I keep a file that tracks the reallocated sector count to see if there is a trend. Some drives will go years without increasing.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-31-2019 08:36 AM                     quote: I always defer this sort of question to the Google whitepaper on HDD failure trends: Thanks John! That's one of the best papers on HDD failure I have ever read. And I'm sure Google is more than qualified to write it. Mark  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 12-31-2019 01:41 PM                     Thanks, everyone. I'll definitely keep a close eye on the drive in question here and if the number of reallocated sectors climbs, I'll just replace it.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 12-31-2019 02:59 PM                        While I agree on the rate of rise of reallocated sectors being a significant indicator, that Google paper was written in 2007, and the work it draws on goes back as far as 2000. I would be interested to know if a similar study done now would result in the same conclusions. The mechanics of HDDs must have evolved a lot in the last 12 years, not least because in 2007, the average consumer or server hard drive was around 200 to 500 GB; now, it's around 1 to 4 TB, in the same form factor.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-31-2019 03:16 PM                     The date is pretty much irrelevant. We had SMART then and hard drives have not changed that much except for size. And it does not pertain to SSD. Mark  |  IP: Logged

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