Re: Hardware vs Software RAID

"Also sprach Matthew Wakeling:"
> >> Has anyone done some benchmarks between hardware RAID vs Linux MD software
> >> RAID?
...
> > The upshot is I don't really see a difference in performance.
>
> The main difference is that you can get hardware RAID with
> battery-backed-up cache, which means small writes will be much quicker
> than software RAID. Postgres does a lot of small writes under some use

It doesn't "mean" that, I'm afraid. You can put the log/bitmap wherever
you want in software raid, including on a battery-backed local ram disk
if you feel so inclined. So there is no intrinsic advantage to be
gained there at all.

> However, not all hardware RAID will have such a battery-backed-up cache,
> and those that do tend to have a hefty price tag.

Whereas software raid and a firewire-attached log device does not.

Peter