8 aug 2008 kl. 18.44 skrev Mark Wong:
On Fri, Aug 8, 2008 at 8:08 AM, Henrik <henke@xxxxxx> wrote:
But random writes should be faster on a RAID10 as it doesn't need to
calculate parity. That is why people suggest RAID 10 for datases,
correct?
I can understand that RAID5 can be faster with sequential writes.
There is some data here that does not support that RAID5 can be faster
than RAID10 for sequential writes:
http://wiki.postgresql.org/wiki/HP_ProLiant_DL380_G5_Tuning_Guide
I'm amazed by the big difference on hardware vs software raid.
I set up e new Dell(!) system against a MD1000 DAS with singel quad
core 2,33 Ghz, 16GB RAM and Perc/6E raid controllers with 512MB BBU.
I set up a RAID 10 on 4 15K SAS disks.
I ran IOZone against this partition with ext2 filesystem and got the
following results.
safeuser@safecube04:/$ iozone -e -i0 -i1 -i2 -i8 -t1 -s 1000m -r 8k -
+u -F /database/iotest
Iozone: Performance Test of File I/O
Version $Revision: 3.279 $
Compiled for 64 bit mode.
Build: linux
Children see throughput for 1 initial writers = 254561.23 KB/sec
Parent sees throughput for 1 initial writers = 253935.07 KB/sec
Min throughput per process = 254561.23 KB/sec
Max throughput per process = 254561.23 KB/sec
Avg throughput per process = 254561.23 KB/sec
Min xfer = 1024000.00 KB
CPU Utilization: Wall time 4.023 CPU time 0.740 CPU
utilization 18.40 %
Children see throughput for 1 rewriters = 259640.61 KB/sec
Parent sees throughput for 1 rewriters = 259351.20 KB/sec
Min throughput per process = 259640.61 KB/sec
Max throughput per process = 259640.61 KB/sec
Avg throughput per process = 259640.61 KB/sec
Min xfer = 1024000.00 KB
CPU utilization: Wall time 3.944 CPU time 0.460 CPU
utilization 11.66 %
Children see throughput for 1 readers = 2931030.50 KB/sec
Parent sees throughput for 1 readers = 2877172.20 KB/sec
Min throughput per process = 2931030.50 KB/sec
Max throughput per process = 2931030.50 KB/sec
Avg throughput per process = 2931030.50 KB/sec
Min xfer = 1024000.00 KB
CPU utilization: Wall time 0.349 CPU time 0.340 CPU
utilization 97.32 %
Children see throughput for 1 random readers = 2534182.50 KB/sec
Parent sees throughput for 1 random readers = 2465408.13 KB/sec
Min throughput per process = 2534182.50 KB/sec
Max throughput per process = 2534182.50 KB/sec
Avg throughput per process = 2534182.50 KB/sec
Min xfer = 1024000.00 KB
CPU utilization: Wall time 0.404 CPU time 0.400 CPU
utilization 98.99 %
Children see throughput for 1 random writers = 68816.25 KB/sec
Parent sees throughput for 1 random writers = 68767.90 KB/sec
Min throughput per process = 68816.25 KB/sec
Max throughput per process = 68816.25 KB/sec
Avg throughput per process = 68816.25 KB/sec
Min xfer = 1024000.00 KB
CPU utilization: Wall time 14.880 CPU time 0.520 CPU
utilization 3.49 %
So compared to the HP 8000 benchmarks this setup is even better than
the software raid.
But I'm skeptical of iozones results as when I run the same test
agains 6 standard SATA drives in RAID5 I got random writes of 170MB /
sek (!). Sure 2 more spindles but still.
Cheers,
Henke
