gmirror slice insertion, "FAILURE - READ_DMA status=51<READY, DSC, ERROR>"

CyberLeo Kitsana cyberleo at
Sat Nov 1 13:09:28 PDT 2008

Thomas Sparrevohn wrote:
> The error occured after I had the disk for a couple of days - WHat puzzled me was that the drive
> did not do it automatically 

Hard disks will not map uncorrectable bad sectors on read automatically,
as it no longer knows what the contents of that sector should be. In
this instance, the sector is usually remapped during a write.

Given the symptoms of the problem described above, it looks like this
uncorrectable sector is located in a portion of the disk that isn't
touched by FreeBSD's newfs or installation procedure, and would never
have a chance to be written to and corrected. Then, when the mirror sync
occurs (which copies every block verbatim, regardless of whether it's in
use or not) it's choking on that sector and locking up the disk, thus
freezing the OS.

One thing to try prior to RMAing the disk is to fill the entire disk
with zeroes (dd if=/dev/zero of=/dev/ad6 bs=131072 or similar) to give
its firmware a chance to remap all flakey sectors, and rewrite all ECC
information. I do this with every new or freshly acquired disk that's
guaranteed to be empty, to ensure that no surprise errors bite me later
on, as well as to make sure no previous data hangs around.

Fuzzy love,
Technical Administrator
CyberLeo.Net Webhosting
<CyberLeo at CyberLeo.Net>

Furry Peace! -

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