RAID5 on athlon64 machines

[soralx at cydem.org]

> Theoretically the sequential write rate should be same or
> higher than the sequential read rate.  Given an N+1 disk

Seq write rate for the whole RAID5 array will always be lower
than the write rate for it's single disk.

See 'http://en.wikipedia.org/wiki/RAID#RAID_5'

"
 Traditional RAID5
  A1  A2  A3  Ap
  B1  B2  Bp  B3
  C1  Cp  C2  C3
  Dp  D1  D2  D3

[...]
If another block, or some portion of a block, is written on that
same stripe the parity block (or some portion of the parity block)
is recalculated and rewritten. For small writes, this requires
reading the old parity, reading the old data, writing the new parity,
and writing the new data.
[...]
The parity blocks are not read on data reads, since this would be
unnecessary overhead and would diminish performance. The parity
blocks are read, however, when a read of a data sector results
in a cyclic redundancy check (CRC) error."

Timestamp: 0x43EE7046
[SorAlx]  http://cydem.org.ua/
ridin' VN1500-B2