[kwlug-disc] btrfs(raid5) or ext4/mdadm(raid5) ?

[William Park]

On Thu, Jun 04, 2015 at 04:00:52AM +0000, B. S. wrote:
> btrfs uses mdadm / raid5 in exactly the same way ext# uses mdadm / raid5.

You can set it up that way, I guess.  But, I was looking to use raid5
feature that is built into BTRFS, eg.
    mkfs.btrfs -d raid5 /dev/sd{e,f,g}
which eliminates the need for MDADM.

> 
> {RAID5 = data availability, not the same thing as data reliability.
> (At home, lose your drives and you're going to be all over it, beating
> upon it until it's done. So I question whether the complexity of RAID
> brings anything to that party.)}

For the array in question with bad sectors, I need size greater than a
single disks.  So, raid5.

> Last time I was in your situation, disks getting questionable ... I
> bought a replacement disk of such size to replace all and some growth.
> I moved the data over, 'converting' from ext4 to btrfs in the process,
> and haven't looked back since. Once done I redeployed the questionable
> disk, with btrfs, and also have not looked back since. For my own
> sanity, too, I no longer have fs that cross disk boundaries. I just ln
> -s things like /data upon growth.

I did this long ago, but gave up due to maintenance.  I may need to
reconsider.  Thanks for reminder.
-- 
William