Re: Use RAID-6!

[Adam Goryachev <mailinglists@websitemanagers.com.au>]

On 17/04/13 14:27, Robert L Mathews wrote:
> But complete disk death doesn't seem to be the normal failure mode. If
> the failure is spurious, as so many seem to be, and temporarily
> affects an array so that each disk has a different event count, that
> isn't a disaster under RAID 1. If worst comes to worst, you can pick
> one disk to use and pretend RAID doesn't even exist. You don't need to
> get the members to successfully sync into an array to read the data.
> But if each disk in a RAID 5 or RAID 6 array gets a different event
> count, or if the disks refuse to easily assemble into an active array
> for any other reason, all your data is inaccessible until you fix the
> RAID problem. I avidly read the details of every RAID 5 [and 6]
> disaster on the list, and almost every one would be trivially easy to
> fix under RAID 1, with no risk of complete data loss. It's heartbreaking. 
RAID1 of course fails the requirement of a single filesystem that
requires more space than a single disk can provide.

Of course, you can then consider LVM2, multiple mount points, or RAID10
or RAID1 + linear etc.... but most people still prefer to see a single
block device. Dealing with multiple RAID1 and a linear could lead to
more complex issues as well.

In any case, as mentioned previously, the majority of issues are caused
by mis-configuration, if we could add some configuration verification to
mdadm or similar, then we might be able to warn more people prior to
things failing.

Regards,
Adam

-- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au