Re: what superblock to use

["H. Peter Anvin" <hpa@zytor.com>]

Mario 'BitKoenig' Holbe wrote:
> Farkas Levente <lfarkas@lfarkas.org> wrote:
>> anyway is there any advantage of a raid6 over raid5+1spare disk? afaik
>> raid5 will be faster and use less cpu and both case 2 disk can failed.
> 
> No, raid6 survives the simultaneous failure of two disks.
> Raid5 survives the simultaneous failure of one disk only. Even with a
> hot-spare, after this failure you have a time frame where the spare is
> synching and your array has no redundancy left. Thus, nearly every other
> disk failure (except a failure on the synching spare) within this time
> frame kills your array.
> 

It's worth noting that a failure mode that is getting increasingly
frequently reported is the failure of a drive *during sync*.  I suspect
that the cause is that synchronization puts different stresses on the
drives than normal operation.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.