Date: Thu, 5 Jul 2018 11:23:01 -0600 From: Alan Somers <asomers@freebsd.org> To: Wojciech Puchar <wojtek@puchar.net> Cc: Stefan Blachmann <sblachmann@gmail.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org>, George Mitchell <george+freebsd@m5p.com>, Lev Serebryakov <lev@freebsd.org> Subject: Re: Confusing smartd messages Message-ID: <CAOtMX2goxJkv1CFAcoFsw0NxaYvmLDXV8CxWr2DuQ%2BD56w2vuw@mail.gmail.com> In-Reply-To: <alpine.BSF.2.20.1807051859250.34332@puchar.net> References: <dfccd275-954c-11da-1790-e75878f89ad1@m5p.com> <51eb8232-49a7-0b3a-2d0f-9882ebfbfa1d@FreeBSD.org> <alpine.BSF.2.20.1807051642090.17082@puchar.net> <CACc-My36jbL=WWpxOB24D_YLDMofSHAk9JgrP86LKd4MEct1mg@mail.gmail.com> <CAOtMX2gG48jzWkPg3kGpSVDC89KY14ta3p-U%2BO5yExHZJfNL7w@mail.gmail.com> <alpine.BSF.2.20.1807051859250.34332@puchar.net>
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On Thu, Jul 5, 2018 at 11:03 AM, Wojciech Puchar <wojtek@puchar.net> wrote: > >> Rewriting suspicious sectors is useless in this day and age. HDDs and >> SSDs >> already do it internally and have for years. Even healthy sectors get >> > > unreadable sectors cannot be rewritten by drive electronics as it doesn't > know what to rewrite. it may possibly remap it but still report read error > until some data will be written - unless giving no error and returning > meaningless data is an accepted behaviour. > But if that disk is already managed by ZFS, the pool is redundant, and the bad sector is allocated by ZFS, then ZFS will immediately rewrite the unreadable sector. > > only on write it can be done properly. > > that the HDD/SSD won't fix itself would be a checksum error. Those are >> > > yes and this will happen if you powerdown your disk on write. or get some > power spike or other source of noise that would affect electronic > components. > It happens surprisingly rarely. Even on a sudden power loss, the drive is usually able to finish its current write operation. When you run into problems would be if the power loss were coincident with a mechanical shock that knocks the head off-track, or something like that. > > performing full disk rewrite (so not zfs rebuilds) and THEN looking at > smart stats and THEN performing regular smartctl -t long will tell the > truth. > > which usually is "drive is fine" in my practice. really faulty drive will > QUICKLY develop new problems. > Yeah, that should make the error go away. It takes a long time, though. With a SCSI drive, you can get the exact LBAs affected with a "READ DEFECTS" command. But there isn't a vendor-independent equivalent for SATA, unfortunately. -Alan
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