Performance factors for HP ProLiant Serial Attached Storage (SAS)

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Figure 11. Random performance comparison between RAID-6 and RAID-5 SFF drives.
Performance comparisons between 6 Gb SAS and 3 Gb SAS
Today’s SAS technology supports a link rate of 6Gb, allowing twice the bandwidth of previous
generation 3Gb technology. Maximum bandwidth of a 6Gb link is 600 MiB/s while a 3Gb link was
limited to a maximum bandwidth of 300 MiB/s. After taking out communication overhead, this
translates to around 500 MiB/s, and 250 MiB/s, actual data transfer rates per link.
Figures 12 and 13 below display sequential read and sequential write performance for RAID-0
arrays. Both arrays reside in an external enclosure, connected to a Smart Array P411 or a Smart
Array P800 controller, by way of a four-lane SAS port.
The P800 controller interface is limited to a 3Gb SAS link rate, while the more recently introduced
P411controller supports a 6Gb SAS link rate.
Benchmark tests performed on RAID-0 array configurations began with just a single 15K SFF drive
and preceded up to an array of twenty-four SFF15K drives (each drive in the tests was capable of
transfer rates of approximately160 MiB/s).
With small arrays of six or less drives, the performance of the P800 and P411 is comparable.
The performance of the P800 controller is limited to a maximum 3Gb link transfer rate, resulting with
array performance only scaling from one to eight drives. For arrays greater than eight drives the
50%
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100%
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130%
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150%
4KiB RAN
READ Aligned
4KiB RAN
WRITE Aligned
4KiB OLTP
Aligned
64KiB RAN
READ Aligned
64KiB RAN
WRITE Aligned
1MiB RAN
READ Aligned
1MiB RAN
WRITE Aligned
Relative Performance - ( % )
1x10-Drv, P411, fw:3.50, 512MB, R6(256KB), 1-D2700, 1LD
1x10-Drv,P411,fw:3.50,512MB,R6(256KB),1-D2700, 1LD
RAID-6 vs RAID-5, Random Performance
10-146GB 15K 6Gb SFF SAS, P411
100%= RAID-5