[Wylug-discuss] Help needed with 'failed' Linux software RAID 10

[John Hodrien]

On Sat, 26 Jun 2010, Martyn Ranyard wrote:

> Okay, that seems off on a huge tangent, but what it seems you might be
> looking for is a (somewhat manual) version of that - RAID for data that's
> not archivable and cache-backed archive for stuff you want ready access to
> but doesn't warrant the cost (and headaches that you've experienced twice
> already) of raid.

Cost of low-grade RAID to protect against a single disk loss just isn't that
high though.  If you're looking at 10Tb with a six disk RAID5 setup, you're
only costing yourself 1 disk, and if you're using software RAID and you're
motherboard's got enough SATA connectors, no other extra costs.  For 100 quid,
you might as well cover yourself.

Given the type of data, I think I'd also consider splitting the filesystems up
far more.  Whatever the cause of the raid problems, if you've got 10
filesystems split across 10 different mdraid devices over the same 6 disk
setup, a loss of a disk loses you nothing, and a screwup in the raid metadata
would cause you grief for 10% of your data.  Given that most of this data is
an archive, most of those filesystems could be routinely mounted read-only,
massively reducing the likelihood of hardware/ram/cpu glitches trashing your
data.

jh