Re: mdadm --fail doesn't mark device as failed?

[Sebastian Riemer <sebastian.riemer@profitbricks.com>]

On 22.11.2012 10:43, Sebastian Riemer wrote:
> On 21.11.2012 20:41, Ross Boylan wrote:
>> On Wed, 2012-11-21 at 18:47 +0100, Sebastian Riemer wrote:
>>
>>> Yes, sometimes hardware has only a short issue and operates as expected
>>> afterwards. Therefore, there is an error threshold. It could be very
>>> annoying to zero the superblock and to resync everything only because
>>> there was a short controller issue or something similar. Without this
>>> you also couldn't remove and re-add devices for testing.
>> So if my intention is to remove the "device" (in this case, partition)
>> across reboots is using sysfs as you indicated sufficient? 
> Yes, if you set a high number into sysfs file "errors", then you can
> even keep the superblock but don't ask me how to revert this change. I
> don't think that there is a "MakeGood" command.
>
>> Zeroing the superblock (--zero-superblock)?
> That's the alternative but you loose superblock data.
>
>>  Removing the device (mdadm --remove)?
> Here you need one of the methods above additionally.

Correction: This also tiggers that the device isn't assembled again
after setting it faulty.

There is a difference in --faulty, --stop and --faulty, --remove, --stop.

>> In this particular case the partition was fine, and my thought was I
>> might add it back later.  But since the info would be dated, I guess
>> there was no real benefit to preserving the superblock.  I did want to
>> preserve the data in case things went catastrophically wrong.
> You don't really have a benefit of keeping the superblock. The only
> useful information is to which device it belonged to. In general you
> replace the failed drive and the new device is synced from the remaining
> good drive. Without the superblock you can read the actual data anyway
> starting from the data offset.
>