[OT] Useable BIOS RAID 1 on the cheap?

Dirk Koopman djk at tobit.co.uk
Tue Jan 17 16:37:48 GMT 2006

On Tue, 2006-01-17 at 15:00 +0000, David Cantrell wrote:
> On Tue, Jan 17, 2006 at 02:26:17PM +0000, Toby Corkindale wrote:
> > On Thu, Jan 12, 2006 at 06:21:12PM +0000, Jacqui Caren wrote:
> > > Steve Mynott wrote:
> > > >I guess my best bet might be the 3ware cards but they are expensive.
> > > I saw an IDE raid controller card at maplin for 20UKP (in a "sale" 
> > > bucket). I assume these are part hard and part soft.
> > Most budget RAID controllers (including just about all the IDE ones) are
> > fairly crappy.
> > 
> > IMHO, you are far better off using software RAID under Linux. Especially when
> > combined with LVM, when the combo becomes *really* nifty.
> Software RAID is great if you have a limited budget, but it is VERY
> slow.  So slow that it can't keep up with an 802.11b network even on a
> pretty reasonable machine.

Er.. It may be a year or five since you benchmarked this yourself, but
more current numbers tend to give the opposite view.

The issues are largely processor speed and buffer space. A hardware raid
device tends to have a rather slow (4-800mhz), otherwise obsolete part
(eg i860) as processor with a smallish amount of RAM. Compare this with
a modern processor of 2+Ghz and the huge sizes of RAM you get in
workstations (never mind servers) these days. Not to mention fairly
close integration of RAID software and kernel buffer cache.

With such differences in hardware power, it doesn't cause huge surprises
when bonnie++ comes back with software v hardware raid 0 throughput
differences of more than 5 to 1. And that was 2 years ago. 

A friend of mine is a disc speed freak and he is reporting bonnie++
throughputs of 110MB / sec read speeds (slightly less on write) on a
three disk software raid 0 setup (AMD 64 3500, 1GB RAM, 3 Seagate
Barracuda 300Mb SATA/150, NVidia chipset). 


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