Re: Migrating a RAID 5 from 4x2TB to 3x6TB ?

[Pierre Wieser <pwieser@trychlos.org>]

---- Original Message -----
> On 08/06/15 21:28, Pierre Wieser wrote:
> > Hi all,
> > 
> > I currently have an almost full RAID 5 built with 4 x 2 TB disks.
> > I wonder if it would be possible to migrate it to a bigger RAID 5
> > with 3 x 6TB new disks.
> 
> I'd recommend against it:
> 
> https://en.wikipedia.org/wiki/RAID#Unrecoverable_read_errors_during_rebuild

Oop's! I was not conscious at all of this issue. It happens that I am currenly
living dangerously as I have another RAID 5 11,5 TB device :( I had already
seen various administration issues when the size increases to this level, but
I tought this was only an issue regarding the volumes organization (not tought
deeply enough, obviously)....

Starting from your link, and searching a bit, I understand now that the 10TB
is a maximal limit for desktop-grade disks (regarding the URE at least). And
thus for any element of a RAID device which needs to be scanned at recovery
time.
Apart from my poor english, would you say I'm right with this ?

Does linux-raid have any recommandation(s) when managing more than 10TB of data ?

I may imagine:
- several smaller RAID 5 devices
- would RAID10 be a valuable solution in your opinion ?

(as a precision, all my servers have been migrated to CentOS 7.1)

Nonetheless, I thank you very much for the link, which may prevent me to
lose a big bunch of data !

> Jan
> 
Pierre