Technical data

White Paper ⏐Performance Report PRIMERGY TX150 S6 Version: 5.1, November 2008
the shorter latency times. Here again the RAID 0 array achieves almost twice the write throughput through parallel ac-
cesses, as compared with the other two configurations.
Enabling the disk cache leads to an increase in
throughput during random access. However this
increase is not as noticeable as with sequential
writing. With a random access with 64 KB blocks
and a single disk configuration the increase in
throughput is about 36%, in RAID 0 about 22%
and in RAID 1 about 19%.
In the case of random access with 8 KB blocks
the increase in throughput is a little higher than in
the case with random access with 64 KB blocks
and is roughly 23% with single disk, 36% with
RAID 0 and about 20% with RAID 1.
The onboard SATA RAID ICH9R controller does not have a controller cache. This fact becomes particularly evident
during write access in RAID 5. The enabling of this disk cache only brings about a moderate increase in throughput of
about three-fold. Measurements with the LSI MegaRAID
SAS 1078 controller, which has a controller cache, have
shown that as a result of the enabled controller cache
throughput increases of up to 39-fold and more are possi-
ble. On the other hand with RAID 10, which actually con-
sists of two »striped« RAID 1 arrays, the enabling of the
disk cache fully benefits write throughput, which increases
by ab
out 13-fold.
cks.
In contrast, the disk cache has no impact on the through-
puts for sequential read with 64 KB blo
In RAID 10 better throughputs are achieved than in RAID 5.
For sequential read access with 64 KB blocks and enabled
disk cache the throughput is about 18% higher. The
throughput is about 6.7-fold higher for sequential write
access with 64 KB blocks and enabled disk cache. The
disadvantage of RAID 10 compared with RAID 5 lies in the
poorer capacity utilization. The loss of capacity in a configuration with four hard disks is 50% with RAID 10 and only 25%
with RAID 5.
The throughput differences between RAID 5 and RAID 10
are also evident during random access. However, these
differences are not as prominent as with sequential write.
The throughput difference between RAID 5 and RAID 10
depends on the block size. For random access with 8 KB
blocks the throughput in RAID 10 is 25% higher and with 64
KB blocks about 14% higher than in RAID 5. For random
access the enabling of the disk cache brings about a
throughput increase of between 27% and 39% with
RAID 10 and about 24% with RAID 5. The slightly poorer
throughputs measured in the RAID 5 array can be ex-
plained through the additional outlay required during the
creation of the parity block.
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