bad sector in gmirror HDD
freebsd at jdc.parodius.com
Sat Aug 20 19:17:31 UTC 2011
On Sat, Aug 20, 2011 at 08:43:09PM +0200, Alex Samorukov wrote:
> >"The SMART tests you did didn't really amount to anything; no surprise.
> >short and long tests usually do not test the surface of the disk. There
> >are some drives which do it on a long test, but as I said before,
> >everything varies from drive to drive."
> It is not correct statement, sorry. Long test trying to read all the
> data from surface (and doing some other things).
> // one of the smartmontools developers and sysutils/smartmontools
That's great, but too bad it's generally not true in practise. Dan's
long scan on his site proves it, and I've dealt with this situation
myself many times over.
SMART long tests *may* do a surface scan, but in most cases they just
seem to do something that's similar to "short" but over a longer period
of time. Furthermore, some which *do* do a surface scan on a "long"
test don't always report LBA failures in the self-test log. I've
personally seen this happen on Western Digital disks (model strings are
unknown, I'm certain I've rid myself of those drives). Firmware
bug/quirk? Possibly, but at the end of the day it doesn't matter -- it
means the end-user has wasted 2-3 hours for something that tests OK yet
we know for a fact isn't OK.
I *have* seen a drive do a surface scan on a "long" test and report LBAs
it couldn't read, but as I said, it's rare and varies from vendor to
vendor, drive to drive, and firmware to firmware. When it happened I
was very, very surprised (and delighted).
The only thing I can trust 100% of the time when it comes to surface
scans is SMART selective scans (if available, which again the OP's drive
does not offer this), or using dd or a read-per-LBA on the OS level
(which works everywhere).
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, US |
| Making life hard for others since 1977. PGP 4BD6C0CB |
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