1 file system, 2 drives?
nightrecon at hotmail.com
Tue Jul 27 14:39:43 UTC 2010
>> If you have hardware controller with RAID capabilities, using native RAID
>> is better, otherwise look towards gvinum or maybe ccd; see also:
> I dont agree that hardware raid is necessarily better. It really depends
> on what the system is doing. If for example it is purely acting as a filer
> I would always use software raid. The main reason for this is that you
> benefit from the faster CPU, and more intelligent raid software (zfs). You
> are also not tied to a particular hardware platform which makes future
> upgrades easier.
In the bad old days (early) days hardware RAID was clearly better. This is
not as true today as CPUs have scaled. The 3GHz plus quad cores of today
have cycles to spare and can actually make software RAID faster in many
situations. The questionable area would be RAID 5 and 6. The XOR processing
done in the hardware controller is expensive, and hardware RAID is still
probably a better way to go here.
Other features such as hot swap, hot spare, scrubbing, and
maintenance/monitoring utilities will be easier to find in the hardware RAID
> If however the system is doing lots of other things and you dont want the
> overhead of a software raid solution, it makes sense to offload it to a
> hardware solution
Very expensive controllers are expensive because the processor on the card
has more horsepower, which typically shows up in IO/s numbers as well as
throughput as multi-thread queue depths rise.
It is a shame to need to spend serious money on these cards just to get the
inherent raw processor power even though you may turn off the RAID
functionality and instead use ZFS and raidz. There is still a performance
advantage to be seen because of the higher processing power available from a
controller processor that has bigger umphh.
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