Hi all,
We are using EVMS 2.5.4 on Linux 2.6.12.6 kernel version.
We find that kernel modules are available for RAID0, 1, 5, 1+0 as part of
this kernel. But however, we do not find a similar module available for RAID
5+0. Can someone advise us of how we would be able to get this support added
into the kernel? If this is not required as a kernel module, how do we
create a RAID 5+0 using MD?
Thanks in advance for your help,
Govind
On Jan 19, 2006, at 11:52, govind raj wrote:
> Hi all,
>
> We are using EVMS 2.5.4 on Linux 2.6.12.6 kernel version.
>
> We find that kernel modules are available for RAID0, 1, 5, 1+0 as
> part of this kernel. But however, we do not find a similar module
> available for RAID 5+0. Can someone advise us of how we would be
> able to get this support added into the kernel? If this is not
> required as a kernel module, how do we create a RAID 5+0 using MD?
Raid math:
RAID(5+0) == RAID(5) + RAID(0)
Commands:
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sda /dev/sdb /
dev/sdc
mdadm --create /dev/md1 --level=5 --raid-devices=3 /dev/sdd /dev/sde /
dev/sdf
mdadm --create /dev/md3 --level=0 --raid-devices=2 /dev/md0 /dev/md1
I believe this is all amply documented on a variety of md websites.
Cheers,
Kyle Moffett
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCM/CS/IT/E/U d- s++: a18 C++++>$ ULBX*++++(+++)>$ P++++(+++)>$ L++++
(+++)>$ !E- W+++(++) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+ PGP
+ t+(+++) 5 X R? !tv-(--) b++++(++) DI+(++) D+++ G e>++++$ h*(+)>++$ r
%(--) !y?-(--)
------END GEEK CODE BLOCK------
Why on earth would you want to stripe two raid-5's instead of using one
raid-5 that is twice as big? You'd get more usable disk space that way.
govind raj wrote:
> Hi all,
>
> We are using EVMS 2.5.4 on Linux 2.6.12.6 kernel version.
>
> We find that kernel modules are available for RAID0, 1, 5, 1+0 as part
> of this kernel. But however, we do not find a similar module available
> for RAID 5+0. Can someone advise us of how we would be able to get
> this support added into the kernel? If this is not required as a
> kernel module, how do we create a RAID 5+0 using MD?
>
> Thanks in advance for your help,
>
> Govind
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>
On 2006-01-19T12:26:10, Phillip Susi <[email protected]> wrote:
> Why on earth would you want to stripe two raid-5's instead of using one
> raid-5 that is twice as big? You'd get more usable disk space that way.
If redundancy is the goal - to be able to withstand two drive failures
-, RAID6 would be the considerably better choice.
Sincerely,
Lars Marowsky-Br?e
--
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business -- Charles Darwin
"Ignorance more frequently begets confidence than does knowledge"
On Thu, 19 Jan 2006, Phillip Susi wrote:
> Why on earth would you want to stripe two raid-5's instead of using one raid-5
> that is twice as big? You'd get more usable disk space that way.
Speed is the issue here, I believe. By stripping two RAID-5 arrays you
ought to get the reliability of the RAID-5 but with considerably higher
speed. That's basically why RAID-50 exists, I think.
Martin
Martin Drab wrote:
> Speed is the issue here, I believe. By stripping two RAID-5 arrays you
> ought to get the reliability of the RAID-5 but with considerably higher
> speed. That's basically why RAID-50 exists, I think.
One big raid-5 would have higher speed because it would have one more
disk allocated to storing data rather than more parity. The raid 5+0
isn't really going to be any more reliable because it can withstand a
single failure in either half, but not two failures in one half, so in
the face of a double failure, you have a 50/50 chance of one being in
each half.
On Thu, 19 Jan 2006, Phillip Susi wrote:
> Martin Drab wrote:
> > Speed is the issue here, I believe. By stripping two RAID-5 arrays you ought
> > to get the reliability of the RAID-5 but with considerably higher speed.
> > That's basically why RAID-50 exists, I think.
>
> One big raid-5 would have higher speed because it would have one more disk
> allocated to storing data rather than more parity. The raid 5+0 isn't really
> going to be any more reliable because it can withstand a single failure in
> either half, but not two failures in one half, so in the face of a double
> failure, you have a 50/50 chance of one being in each half.
Well, yes and no. See for instance:
http://en.wikipedia.org/wiki/RAID#RAID_50_.28RAID_5.2B0.29
Martin