Best software raid 5 software?
John Nielsen
lists at jnielsen.net
Wed Mar 21 14:32:32 UTC 2007
On Wednesday 21 March 2007 03:03:53 am Gabriel Rossetti wrote:
> I am about to switch to software raid 5 for my personal server. I know
> hardware raid 5 is better, but being a student I'd rather not invest in
> a raid adapter now, plus my cpu is being used at about 0.0% 24/24 7/7,
> so it needs some exercise :-)
>
> I've heard of several software-based raid-5 projects, mainly of Vinum,
> has anybody tested it or any other ones?
> Which would you suggest?
As far as I know, gvinum is the only software package in FreeBSD that can do
RAID 5. The initial learning curve is a bit steep, but it should work fine
once you get it configured.
I would also suggest that you look at graid3 which, not surprisingly, supports
RAID 3. As you may or may not know, RAID 3 is very similar to RAID 5. You get
S*(N-1) usable space, where S is your disk size and N is the number of disks.
You need at least three disks but can use more. Both allow you to lose any
single disk and not lose any data. The difference is that RAID 5 stripes the
redundant parity data across all of the disks and RAID 3 uses a single disk
for all parity writes. As a result, RAID 5 potentially offers somewhat better
read performance if disk I/O is the bottleneck (and assuming each disk has
its own controller/I/O path). In the case of software raid and commodity
(non-server) hardware, the difference should be nominal.
Other software RAID options include gmirror (recommended for RAID1), gstripe
(recommended for RAID0, can be combined w/ gmirror), ataraid (supports RAID0,
RAID1, JBOD, and combinations on ata controllers only), and ccd (supports
RAID0, RAID1, and JBOD; largely deprecated by gmirror and gstripe).
JN
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