<quote who="O Polite">
> On Fri, 2002-02-22 at 02:16, Alvin Oga wrote:
>
>> if you can write data to /dev/hda1 in 5 seconds...
>> writing to striped raid0 will be say 7-10 seconds...
> Why is this? I thoght the point of raid0 was to write to all drives
> in parallell.
it is, and there is a decent performance improvement
in software raid under 2.2, i think i have read somewhere
that performance is dramatically down in kernel 2.4(don't
remember which kernel it was referring to).
just doing a crude test, i get approx 100% performance
increase in writes from raid0 compared to no raid.
one of my servers is running 3 x seagate ST39204LW
Ultra160 10,000RPM drives. 2 are in raid0 and 1 is
not.
this is for a 477MB file.
non raid:
mail:~# time dd if=/dev/zero of=testfile bs=100000 count=5000
5000+0 records in
5000+0 records out
real 0m10.035s
user 0m0.020s
sys 0m2.060s
raid0:
mail:/var/spool# time dd if=/dev/zero of=testfile bs=100000 count=5000
5000+0 records in
5000+0 records out
real 0m5.156s
user 0m0.030s
sys 0m2.690s
earlier in the year i ran bonnie on my servers and
heres some quick stats
Dual P3-800 512MB, 2xSeagate drives in raid0:
200MB - Block Writes - 95,826kB/second
Block reads - +++++ kB/second (don't know why bonnie
did that)
no raid, same system
200MB - Block writes - 52,739kB/second
- Block reads - +++++ kB/second (again, weird)
Dual P3-733 256MB RAM, similar drives, running in raid1:
200MB - Block writes - 41,243 kB/second
Block reads - 195,953 kB/second
All filesystems ext2, all kernels 2.2.19
nate
