Re: hardware raid vs. software raid
On Thu, 30 Nov 2006 15:44:38 +0100, Johannes Wiedersich wrote
> Preparing to buy a new server...
>
> What is debian's opinion about hardware/software raid?
>
> I have the feeling that software raid 1 is more reliable since if
> anything goes wrong with the hardware, I could just take one or two
> disks out of the server and put them into a workstation to get up and
> running or copy data of the disks for the time until the hardware
> gets fixed.
>
> On the other hand, performance will probably be better with a dedicated
> hardware raid controller.
>
> What are your experiences?
I'm a huge fan of software raid.
I think reliably, they are probably the same.
I prefer SW raid for its lower cost, and its ability to warn you of a failing
disk via email. HW raid will only yell at you if somethings wrong, (maybe expensive HW raid
has email features, but I'm not aware of any)
I find the mdadm tool very good at customizing your arrays too. Lots of flexability.
For performance, I'm not so sure any more that HW raid is faster. Even if the server is under load.
>From some basic bonnie++ tests on an LSI Raid controller compared to SW raid on a 2 x Xeon
system running Sarge, the SW raid 5 was faster. Sorry I don't have any actual stats.
and others may have stats that show different.
If possible, you could try and benchmark the system before you decide, but I don't know if you can
"borrow" a raid controller to perform your tests. Maybe your vendor will let you return it if you don't
like the results.
Another problem however, is finding a MB with lots of disk controllers. You can easily get Raid
controllers with 8 or more sata ports, but server boards usually have 2 or 4. Although recently, you
can get intel boards with 6 on board Sata controllers. Depends on your setup I guess.
Further, I'm more in favor of Raid 10 systems, for systems that do lots of different tasks.
Raid 5 begins to really slow down when your system is under stress.
There's tons of comparisons of which raid to use on google. You get to decide which one is best for
you. :)
Cheers,
Mike
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