Re: SMART detects pending sectors; take offline?

[Wols Lists <antlists@youngman.org.uk>]

On 07/10/17 11:05, Alexander Shenkin wrote:
> Thanks Carsten,
> 
> I was mistaken, it's a RAID1, not RAID0.  I have /boot mounted on a
> RAID0, and / mounted on RAID5.  They both split across 4 drives.

How big is each partition that makes up /boot? If that's raid0, surely
that's not wise? A single disk failure will render the machine
unbootable. Surely that should be raid1, so you can boot off any disk.
> 
> Appreciate the advice - i'll just keep it running until the drive
> arrives tomorrow...

I'd keep it running ...
> 
> Thanks,
> Allie
> 
> On 10/7/2017 9:21 AM, Carsten Aulbert wrote:
>> Hi
>>

>>
>> Given this is "only" a single sector error I would keep it running as
>> long as you can physically install the new drive and only then take it
>> offline.
>>
>> At least theoretically, it may be possible to force the rewrite of this
>> sector and use the spare sectors of the disk, but I'm not 100% sure if a
>> simple md check would already trigger it - usually you need to write
>> "new" data to defective sectors to force the drive's firmware to use the
>> spare sectors.
>>
How serious is a "pending sector"? I think doing a scrub will fix it.

If it's not serious I'd look at using the extra drive to convert it to
raid6. I doubt the infamous 3TB drives were a "bad batch", but given the
press they got I would have expected Seagate to fix the problem. If
these drives are newer than the ones that got the bad press, they might
be fine.

There's always the argument "do you ditch a disk on the first error, or
do you wait until it's definitely dying". But iirc a "pending sector" is
just one of those things that happens every now and then. If this goes
away with a scrub, and you don't get a batch of new ones, then the drive
is probably fine (until the next *random* problem shows up).

Cheers,
Wol