In the last episode (Aug 21), Jon Drukman said:
> Lefevre, Steven wrote:
> >I say go with RAID 5, on a controller card.
> > Mirroring just gives you backup, and you lose half your diskspace.
> > It offers no performance benefit, and actually the computer might
> > have to work harder to make sure the drives are in sync.
>
> that is not true. mirroring gives you double the read speed and half
> the write speed. RAID5 gives you less than half the write speed.
Software raid5 gives you around 1/4 the write speed, to be exact.
Hardware raid5 with battery-backed cache can completely remove the
penalty, by either waiting for an entire stripe of data to flush in one
operation, or delaying the extra I/O operations until the disk head
happens to be near that block anyway (or until the disk is otherwise
idle). Make sure you max out the RAM in your raid card; it's cheap.
--
Dan Nelson
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