[mythtv-users] OT Hardware RAID 5 Recommendations

Steven Adeff adeffs.mythtv at gmail.com
Tue Dec 12 21:03:47 UTC 2006


On 12/12/06, Paul Hamm <paulhamm at verizon.net> wrote:
> Interesting ran this on my machine.  See the bottom for PC specs.  The
> system is running 2 instances of FAH.  Not a very consistent test.
> Using a 6 Disk raid 5 array.
>
> [root at blah temp]# time dd if=/dev/zero of=test bs=1M count=1024
> 1024+0 records in
> 1024+0 records out
> 1073741824 bytes (1.1 GB) copied, 22.3979 seconds, 47.9 MB/s
>
> real    0m22.489s
> user    0m0.004s
> sys     0m4.107s
> [root at blah temp]# time dd if=/dev/zero of=test bs=1M count=2048
> 2048+0 records in
> 2048+0 records out
> 2147483648 bytes (2.1 GB) copied, 36.211 seconds, 59.3 MB/s
>
<snip>
> > >
> > > Thanks, I'm looking for RAID5 which requires that a parity bit be set
> > > across all of the disks.  This requires a fair bit of horsepower.
> > > RAID1 is (if I remember correctly) simply a mirror, which would be a
> > > waste of disk space.  On that point, I'm not sure if software RAID
> > > does level 5.

Interesting test, to add to the benchmarks (these are all the median
of 3 runs each)...
4 disk software RAID 10, (2 SATA 2 ATA/100 on seperate channels, all
identical 300GB Maxtor 7200RPM)
root at mythbackend:/MythTV/tv# time dd if=/dev/zero of=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 7.94951 seconds, 135 MB/s

real    0m7.951s
user    0m0.000s
sys     0m1.808s
root at mythbackend:/MythTV/tv# time dd if=/dev/zero of=test bs=1M count=20
48
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 29.0446 seconds, 73.9 MB/s

real    0m29.071s
user    0m0.016s
sys     0m3.604s
root at mythbackend:/MythTV/tv# time dd of=/dev/zero if=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 24.9988 seconds, 85.9 MB/s

real    0m25.128s
user    0m0.016s
sys     0m3.580s
root at mythbackend:/MythTV/tv# time dd of=/dev/zero if=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 9.72357 seconds, 110 MB/s

real    0m9.828s
user    0m0.004s
sys     0m1.768s

3 disk RAID 5 (3x ST373405LC, U160 Seagate Cheetah 10K 73GB on a
Adaptec AHA2940U2W)
root at mythbackend:/Storage# time dd if=/dev/zero of=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 56.9128 seconds, 18.9 MB/s

real    0m56.915s
user    0m0.000s
sys     0m1.632s
root at mythbackend:/Storage# time dd if=/dev/zero of=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 119.552 seconds, 18.0 MB/s

real    1m59.572s
user    0m0.008s
sys     0m3.124s
root at mythbackend:/Storage# time dd of=/dev/zero if=test bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 31.2467 seconds, 34.4 MB/s

real    0m31.356s
user    0m0.008s
sys     0m1.696s
root at mythbackend:/Storage# time dd if=/dev/zero of=test bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 119.552 seconds, 18.0 MB/s

real    1m59.572s
user    0m0.008s
sys     0m3.124s

sadly pathetic. time to replace these with some newer SATA drives...

I also have a 3 disk RAID 5 made from 250GB ATA/100 drives on my
frontend which is currently off, and I'm at work so I can't test
them...

-- 
Steve
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