Technical data

White Paper ⏐Performance Report PRIMERGY TX150 S6 Version: 5.1, November 2008

The following graphic shows that during random access in RAID 1 the combination of the “Write-back” and “Disk cache

enabled” options has a decisive influence on throughput. The improvement in throughput is 48% or 56%, depending on

whether access is with 64 KB or

8 KB block size.

LSI MegaRAID SAS 1078 with 512 MB Cache, 2.5" 15 krpm Hard Disks

For random access in RAID 5 it is

advisable to enable the controller

cache by setting the write-mode

option to “Write-back”. In order to

achieve optimal throughput it is also

necessary to enable the disk cache.

As a result of these optimal cache

settings improvements in throughput

of 54% or 60% can be achieved,

depending on the block size used.

More detailed information about this topic is available in the paper

Performance Report - Modular RAID for PRIMERGY.

Controller comparison

The following comparison depicts the throughputs of the various controllers. The measurements were made with the

same hard disk types in the same RAID 1array. The diagram shows the throughputs achieved with disabled caches (Off)

and with optimal cache settings

(Optimal).

You can see that the cache set-

tings for sequential read access

do not have any or only a very

minor influence on throughput,

regardless of which controller is

used. The throughput values

achieved are equivalent to the

maximum possible values. For

sequential write access it is pos-

sible to achieve an increase in

throughput by optimizing the

cache settings. Throughput in-

creases by about 66% with the

LSI MegaRAID SAS 1068 con-

troller. The best throughput val-

ues were achieved with the LSI

MegaRAID SAS 1078 controller

with a 512 MB controller cache.

The difference in performance to

the LSI MegaRAID SAS 1078 controller with a 256 MB controller cache is about 3.2% with optimal cache settings and

sequential write access. The difference in performance to the LSI MegaRAID SAS 1068 controller is approximately 2.2%.

If the LSI MegaRAID 1078 controller with 256 MB and 512 MB cache is compared with the LSI MegaRAID 1068 control-

ler during random access with 8KB and 64KB, then the throughput difference is between 5 and 6.5%.