An Investigation into Transport Protocols and Data Transport ...

A.1. Data Storage 272
Number RAID-0 (Mbit/sec) RAID-5 (Mbit/sec)
Controller Type of Disks Read Write Read Write
ICP 33 4 751 811 686 490
ICP 66 4 893 1,202 804 538
3W-ATA 33 4 1,299 835 1,065 319
3W-ATA 66 4 1,320 1,092 1,066 335
3W-ATA 33 8 1,344 824 1,280 482
3W-ATA 66 8 1,359 1,085 1,289 541
3W-SATA 66 4 1,343 1,116 1,283 372
3W-SATA 66 8 1,389 1,118 1,310 513
Table A.4: Summary of Read and Write Speeds of 2GB Files for controllers configured
as RAID 0 and RAID 5 with vm.max-readahead=1200.
Generally, the performance of both read and write speeds is aided with
the following configurations:
Tuning of Kernel Parameters It was observed that setting vm.max-readahead
to 1200 helped in all cases. The default value of 31 reduced the performance
of RAID-5 devices by as much as 75% in the case of the 3Ware
SATA tests.
Number of Disks An increase in the number of channels being used in the
RAID helps with the striping of data across hard disks and improves
the read speed as each separate hard disk is able to retrieve a separate
block of the file.
PCI Bus Speed A higher PCI bus speed is recommended, with the greatest
increase in performance achieved with the write performance of the
RAID devices. The performance increase of the 3Ware cards with increased
PCI Bus speed was not as noticeable as that of the ICP cards.
File Size Whilst the read performance remains constant for all file sizes