CentOS - Jan 2023 - Upgrading system from non-RAID to RAID1

Hallo Simon,
> Anyway, the splitting of large disks has additional advantages. Think of
> what happens in case of a failure (power loss, kernel crash...). With the
> disk as one large chunk, the whole disk has to be resynced on restart
> while with smaller segments only those which are marked as dirty have to
> be resynced. This can make a bit difference.
I am not sure if this is true. If a underlying disk fails, it will mark all
partitions on that disk as dirty, so you will have to resync them all after
replacing or readding the disk into the array.

Michael

> Hallo Simon,
>
>> Anyway, the splitting of large disks has additional advantages. Think
of
>> what happens in case of a failure (power loss, kernel crash...). With
>> the
>> disk as one large chunk, the whole disk has to be resynced on restart
>> while with smaller segments only those which are marked as dirty have
to
>> be resynced. This can make a bit difference.
>
> I am not sure if this is true. If a underlying disk fails, it will mark
> all partitions on that disk as dirty, so you will have to resync them all
> after replacing or readding the disk into the array.
No, I'm not talking about a complete disk failure, my example wasn't a
failure at all but a server problem like power loss, kernel crash and such
things. In this case only the segments which were not in sync at the time
of the crash will be resynced on restart, not the whole disk.

The same is, if a read error happens on one disk, only the partial segment
will lose redundancy and not the whole contents of the disk.

That's a huge improvement especially on very large disks.

Simon