Laurent CARON wrote:
Hello,
We are in the process of increasing the size our RAID Arrays as our storage needs increase.
Hi, I'm no expert but I'll bounce some thoughts back at you...
I've got 2 solutions for this:
- Copy the data over a new array and replace the disks
pros:
sane and minimal risk of data loss since you don't delete data until the new one is up.
quickest solution (in manpower, elapsed time and system outages)
cons:
doesn't test Neils grow mode in mdadm (without which none of this would be possible)
- Replace each disk (one after the other(after resync)) of the existing array with a bigger one.
and the corollorary of sane would be... <joke>
This seems like it would work with mdadm's shiny new(?) grow command.
Start: - Array is ok - Remove 1 disk - Array is degraded - Add a bigger disk - Resync - Remove another disk - Array is degraded - Add a bigger disk - Resync .....
It looks from the man page like you use the grow command *after* changing out all the disks; yes?
Shiny and new means you need a reliable backup.
And this is likely to be slow - 1 resync per disk - and needs a system shutdown/outage for each disk swapped (assuming not hot-swap-able)
If you do have hot-swap then this seems like quite a nice option (no outages)
Mad speculative question ... Would doing this work: - add new big disk - mdadm --remove a disk - dd if=<removed disk> of=<new disk> - mdadm -add new disk? - remove small disk
if so it'd be a lot quicker than a resync each time...
Would this be the 'state of the art' way ?
Have you seen EVMS? It has the ability to add devices to a raid5 array.
I'd class that as state of the art since you aren't 'throwing away' the smaller disks.
Will the filesystem cope with it?
yes assuming it has a growfs.
Is my mind completely broken?
not yet - let us know after you try it...
David - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
