From: Paul Jakma (paulj at domain alphyra.ie)
Date: Thu 11 Jul 2002 - 19:47:02 IST
On Thu, 11 Jul 2002, Ronan Cunniffe wrote:
> Did I once hear correctly that the IDE "raid" controllers did all
> the hard work in software - i.e. reading & comparison at the CPU
> rather than an on-card controller? Is that true of all IDE raid
> cards, and if so, what kind of performance hit results? Not just
> CPU load, but PCI load? Anybody?
double edged sword.
Most host CPUs will be much faster than the embedded CPUs found on
hardware RAID cards. Important for RAID5.
The downside is software raid has to send both the data and the
redundant data to the card, ie 2x for RAID1 and 0.5x for 3 disk RAID5.
so for RAID1 you might be better off with software raid, cause it's a
simple job in terms of processing, for RAID5 the benefit of a fast cpu
could easily outweigh the bus overhead. (esp. compared with low-end
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