Re: SMART detects pending sectors; take offline?

From: Alexander Shenkin <al@shenkin.org>
To: Brad Campbell <lists2009@fnarfbargle.com>,
	Reindl Harald <h.reindl@thelounge.net>,
	Phil Turmel <philip@turmel.org>,
	Edward Kuns <eddie.kuns@gmail.com>,
	Mark Knecht <markknecht@gmail.com>
Cc: Wols Lists <antlists@youngman.org.uk>,
	Carsten Aulbert <carsten.aulbert@aei.mpg.de>,
	Linux-RAID <linux-raid@vger.kernel.org>
Subject: Re: SMART detects pending sectors; take offline?
Date: Wed, 3 Jan 2018 13:50:04 +0000	[thread overview]
Message-ID: <07170cf8-d951-013b-7e67-eee54aa60c65@shenkin.org> (raw)
In-Reply-To: <14f1fce1-2959-e051-f7c8-1d98951d744a@fnarfbargle.com>

On 1/3/2018 1:26 PM, Brad Campbell wrote:
> 
> 
> On 03/01/18 20:44, Alexander Shenkin wrote:
>> On 12/23/2017 3:14 AM, Brad Campbell wrote:
>>> On 21/12/17 19:38, Reindl Harald wrote:
>>>>
>>>>
>>>> Am 21.12.2017 um 12:28 schrieb Alexander Shenkin:
>>>>> Hi all,
>>>>>
>>>>> Reporting back after changing the hangcheck timer to 180 secs and 
>>>>> re-running checkarray.  I got a number of rebuild events (see 
>>>>> syslog excerpts below and attached), and I see no signs of the 
>>>>> hangcheck issue in dmesg like I did last time.
>>>>>
>>>>> I'm still getting the SMART OfflineUncorrectableSector and 
>>>>> CurrentPendingSector errors, however.  Should those go away if the 
>>>>> rewrites were correctly carried out by the drive? Any thoughts on 
>>>>> next steps to verify everything is ok?
>>>>
>>>> OfflineUncorrectableSector unlikely can go away
>>>>
>>>> CurrentPendingSector
>>>> https://kb.acronis.com/content/9133
>>>
>>> If they've been re-written (so are no longer pending) then a SMART 
>>> long or possibly offline test will make them go away. I use SMART 
>>> long myself.
>>>
>>
>> Thanks Brad.  I'm running a long test now, but I believe I have the 
>> system set up to run long tests regularly, and the issue hasn't been 
>> fixed.  Furthermore, strangely, the reallocated sector count still 
>> sits at 0 (see below).  If these errors had been properly handled by 
>> the drive, shouldn't Reallocated_Sector_Ct sit at least at 8?
> 
> Nope. Your pending is still at 8, so you've got bad sectors in an area 
> of the drive that hasn't been dealt with. What is "interesting" is that 
> your SMART test results don't list the LBA of the first failure. 
> Disappointing behaviour on the part of the disk. They are within the 1st 
> 10% of the drive however, so it wouldn't surprise me if they were in an 
> unused portion of the RAID superblock area.

Thanks Brad.  So, to theoretically get these sectors remapped so I don't 
keep getting errors, I would have to somehow try to write to those 
sectors.  That's tough given that the LBA's aren't reported as you 
mention.  Perhaps my best course of action then is to:

1) re-run sudo /usr/share/mdadm/checkarray --idle --all
2) add my previously-purchased drive to convert the RAID5 to RAID6 
(using 
http://www.ewams.net/?date=2013/05/02&view=Converting_RAID5_to_RAID6_in_mdadm 
as a guide)
3) after that, fail and remove /dev/sda from the RAID6
4) write 0's on /dev/sda (dd if=/dev/zero of=/dev/sda bs=1M)
5) re-add /dev/sda to the RAID6

This should get those bad sectors remapped...  thoughts?

thanks,
allie