IDE, SATA, RAID0, RAID4, and RAID5

[markw at mohawksoft.com (markw at mohawksoft.com)]

I am lucky enough to have a three mechanically identical drives, one PATA
(EIDE) and two with SATA and took the time to make a few tests:

---- First, IDE vs SATA. ----
(These drives are western digital WD2500JB and WD2500JS)

IDE Hard disk
root at snoopy:/home/markw# time dd if=/dev/zero bs=1M count=8192 of=/dev/hde1
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 145.084 seconds, 59.2 MB/s

real    2m25.090s
user    0m0.044s
sys     0m42.479s

SATA Hard Disk
root at snoopy:/home/markw# time dd if=/dev/zero bs=1M count=8192 of=/dev/sda1
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 127.332 seconds, 67.5 MB/s

real    2m7.337s
user    0m0.048s
sys     0m40.463s

In the above examples, we see that the drives perform similarly, but that
the SATA interface gives an advantage in transfer speeds, but not the
100mb/s vs 300mb/s advertised difference.


---- Second: RAID0 ----

A two drive RAID0 system:
mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sda1
/dev/sdb1

root at snoopy:/etc/init.d# time dd if=/dev/zero bs=1M count=8192 of=/dev/md0
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 67.2203 seconds, 128 MB/s

real    1m7.268s
user    0m0.060s
sys     0m22.117s

Note, almost double the performance with negligible impact on system
processing time.

A three drive RAID0 system:

mdadm --create --verbose /dev/md0 --level=0 --raid-devices=3 /dev/sda1
/dev/sdb1 /dev/hde1

root at snoopy:/etc/init.d# time dd if=/dev/zero bs=1M count=8192 of=/dev/md0
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 47.9306 seconds, 179 MB/s

real    0m48.226s
user    0m0.052s
sys     0m24.646s

Note, a wopping almost 3 time performance boost!!, the system CPU is
increased a bit.

---- Third: A RAID4 system: ----

mdadm --create --verbose /dev/md0 --level=4 --raid-devices=3 /dev/sda1
/dev/sdb1 /dev/hde1

root at snoopy:/etc/init.d# time dd if=/dev/zero bs=1M count=8192 of=/dev/md0
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 125.434 seconds, 68.5 MB/s

real    2m5.839s
user    0m0.040s
sys     0m24.526s


---- Fourth: A RAID5 system ----
mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sda1
/dev/sdb1 /dev/hde1

root at snoopy:/etc/init.d# time dd if=/dev/zero bs=1M count=8192 of=/dev/md0
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB) copied, 129.666 seconds, 66.2 MB/s

real    2m9.675s
user    0m0.028s
sys     0m24.230s

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