[GRLUG] RAID levels

[L. V. Lammert]

On Fri, 30 Sep 2011, Mike Williams wrote:

> Last night at The Warehouse we had a fairly involved discussion about
> the various RAID levels. I realized, while churning it over in my head
> again a little while ago, that one of my assumptions was not quite
> correct. I thought that in RAID 6, since you have an extra drive, that
> the system doesn't need to do parity reconstruction like RAID 5 does
> once you lose the first drive. Since even in RAID 6 there is actual data
> on that drive, it still has to do the reconstruction so you will still
> lose performance once the first drive failed. That being the case, would
> Casey's music box be better off in RAID 5 with a hot spare rather than
> RAID 6 without? RAID 6 has the advantage that the array wouldn't go down
> until the 3rd drive failure,while a RAID 5 array would go down on the
> 2nd. However, under RAID 5 with a hot spare the rebuild of the array
> could start immediately, vastly reducing the time during which the array
> is running in degraded mode. Thoughts?
>
Performance is specific to the HW - are you speaking of software RAID, MB
RAID (aka Fake Raid), or a separate HW RAID controller?

The main reason to clarify is that you are mentioning RAID functionality
not present in kernel-level (soft RAID), i.e. hot rebuild?

	Lee

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.