On Wednesday January 12, gordon@drogon.net wrote:
Until now I haven't really paid too much attention to the RAID-6 stuff,
but I have an application which needs to be as resilient to disk failures
as possible.
So other than what's at:
ftp://ftp.kernel.org/pub/linux/kernel/people/hpa/
and the archives of this list (which I'm re-reading now), can anyone give
me a quick heads-up about it?
Specifically I'm still buried in the dark days of 2.4.27/28 - are there
recent patches against 2.4?
There is no current support for raid6 in any 2.4 kernel and I am not
aware of anyone planning such support. Assume it is 2.6 only.
If RAID-6 isn't viable for me right now, what I'm planning is as follows:
Put 8 x 250GB SATA drives in the system, and arrange them in 4 pairs of
RAID-1 units.
Assemble the 4 RAID-1 units into a RAID-5.
Sounds reasonable.
NeilBrown
On Thu, 13 Jan 2005, Neil Brown wrote:
There is no current support for raid6 in any 2.4 kernel and I am not
aware of anyone planning such support. Assume it is 2.6 only.
How "real-life" tested is RAID-6 so-far? Anyone using it in anger on a
production server?
I've spent the past day or 2 getting to grips with kernel 2.6.10 and mdadm
1.8.0 on a test system running Debian Woody, on a rather clunky old test
PC - Asus XG-DLS, Twin Xeon PIII/500's on-board IDE with 2 x old 4GB
drives attached, it also has on-board Adaptec SCSI with 2 x 18GB drives -
one on an 8-bit bus, and a Highpoint HPT302 card with 2 modern 80 GB
drives (Maxtor, I know, but keep them cool and so-far so good...)
Performance isn't exactly stellar (one PCI bus!) but I did squeeze
60MB/sec out of a RAID-0 off the 2 new drives... Clunky by todays
standards, but 5.5 years ago when it was new, it rocked!
Anyway, so far so good. I've constructed a RAID-6 system with a 4GB
partition on 5 of the drives, and done some tests & what not.
The tests I've done involve creating the array, putting a filesystem on it
(ext3), writing a bigfile of zeros, checksumming it, failing a drive,
adding it back in, failing another, failing a 2nd, adding them in, failing
another before the 2nd drive finished resyncing, etc. all the time writing
a file & checksumming it between unmounting & re-mounting it. There was a
script posted round about July last year which I used to get some ideas
from.
So-far so good, no corruption, but it doesn't doesn't mean anything in the
real-world.
So who's using RAID-6 for real?
Can it be considered more or less stable than RAID-5?
Should I stick to my RAID-5 on-top of RAID-1 pairs?
Or should I just take a chance with RAID-6? (And nearly 6 years ago when I
started using Linux s/w RAID I said this to myself, but stuck with it and
haven't had a problem I could pin down to software... So who knows!)
Gordon