Ominous smartd messages ....

[Jon Radel]

On 8/2/16 11:41 PM, William A. Mahaffey III wrote:

> It has 8 1 TB HDD's in a ZFS unmirrored pool. 

Do I understand this to mean you have 8 TB with no redundancy?  Pretty
brutal if your data starts rotting away.  :-(



> Aug  1 23:09:59 devbox smartd[835]: Device: /dev/ada5, 8 Currently
> unreadable (pending) sectors


> 
> My question is: Are these messages benign, or am I in the market for
> more hardware ? *ANY* more questions, please ask. TIA & have a good one.
> 

Somewhere between, YMMV, depends on your luck and the phase of the moon.
 That's useless, so I'll expand:

I've read reasonable sounding commentary from people running very, very
large collections of hard drives that there is a high enough correlation
between this error and the drive going to heck sooner rather than later
that they take this as a sign to replace.  [Can't find reference right now.]

I've read reasonable sounding commentary that by writing to the bad
sector(s) you can force the HD to reallocate the sectors (assuming
remaining capacity to do that) and then use ZFS redundancy and a good
scrub to recover the data you trashed with dd (might not apply to you).
Then there's a good chance that all will be well indefinitely.  See
https://dekoder.wordpress.com/2014/10/08/fixing-freenas-currently-unreadable-pending-sectors-error/
for an example of this school of thought.  Actually, given that the
messages stopped again, I suspect reallocation already happened, but a
smartd test should tell you for certain.  (You didn't have a scrub
running between 8/2 03:39 and 04:09 by any chance?)

Personally, so long as only one drive in my pool is doing this I tend to
replace but not rush.  I'd rush more if the sector count started
creeping up, up, up.

-- 
--Jon Radel
jon at radel.com

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