Re: Requesting assistance recovering RAID-5 array

Phil Turmel
2020-04-01T12:55:02Z

On 4/1/20 8:15 AM, Wols Lists wrote:
> On 01/04/20 07:03, Daniel Jones wrote:
>> Thanks Phil,
>>
>> I'll read this a couple of times and try some commands (likely on an
>> overlay) tomorrow.
>
> If you CAN overlay, then DO. If you can't back up the drives, the more
> you can do to protect them from being accidentally written to, the better.

I have to admit that I pretty much never use overlays. But then I'm
entirely confident of what any given mdadm/lvm/fdisk operation will do,
in regards to writing to devices. And since it is burned into my psyche
that raid is *not* backup, only an uptime aid, I keep good external
backups. (:

Lacking confidence and lacking backups are both good reasons for using
overlays. I'm not entirely sure the mental effort for a novice to learn
to use overlays is time better spent than learning enough about MD and
mdadm for confident use.

I do think initial recovery efforts with --assemble and --assemble
--force do not need to be done with overlays. They are so safe and so
likely to quickly yield a working array that I think overlays should be
recommended only for invasive tasks needed after these --assemble
operations fail.

--create is a very invasive opertion.

Phil