[Discuss] SW vs HW raid (was raid controller drivers)

[blu at nedharvey.com (Edward Ned Harvey (blu))]

> From: jabr at gapps.blu.org [mailto:jabr at gapps.blu.org] On Behalf Of John
> Abreau
> 
> I think I see it now. I said I prefer software raid over hardware raid, and your
> response is that zfs software raid is preferable to hardware raid.
> 
> So basically, you're disagreeing with the same arguments that I was
> disagreeing with, and I misread it as you disagreeing with my argument.

Hehhehe, it's a little bit more involved than just "hardware is better than software" or vice-versa.  Each one has its own pros and cons.

Zfs does both performance optimizations as well as reliability enhancement in software, which cannot be done by hardware.

Btrfs does reliability enhancement better than hardware, but I don't think they match zfs for performance enhancement.  If I'm not mistaken, btrfs soft-raid on top of an HBA with write-back gets you the best you can get out of btrfs, which is good but still not quite on par with zfs.

Assuming a good accelerating HBA with write back, hardware raid with a non-raid filesystem such as ExtFS, or NTFS, is faster than md-raid or windows soft raid.  So HW raid is preferred over them.

Don't forget also, there are hardware raid solutions out there that don't do write-back, so they tend to be even slower than crappy software raid...

And there's a gray area of what you even count.  There's the whole class of BIOS fake raid which ...  I never quite got.