An Investigation into Transport Protocols and Data Transport ...

A.1. Data Storage 269
Read Speed (Mbit/sec)
1600
1400
1200
1000
800
600
400
vm.max-readahead 31
vm.max-readahead 63
vm.max-readahead 127
200
vm.max-readahead 256
vm.max-readahead 512
vm.max-readahead 1200
0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
File Size (MBytes)
Write Speed (Mbit/sec)
1600
1400
1200
1000
800
600
400
200
vm.max-readahead 31
vm.max-readahead 63
vm.max-readahead 127
vm.max-readahead 256
vm.max-readahead 512
vm.max-readahead 1200
0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
File Size (MBytes)
(a) Read Performance
(b) Write Performance
Figure A.5: Performance for 3Ware SATA (RAID 5 with 4 Disks and 66Mhz PCI).
disks. The 3Ware controllers are able to hold up to 8 disks. The read and
write speeds for the 3Ware cards were greatly enhanced when 8 disks were
included in the array as demonstrated in Figure A.6 as well as Table A.4.
An ICP GDT8586RZ 8 channel array could not be obtained, and therefore
equivalent testing was not possible.
Figure A.5 shows results for the 3Ware-SATA RAID controller configured
as RAID-5. This card has a 66 MHz PCI bus; an equivalent 33 MHz version
was not available for testing. The read speeds for this controller were the
fastest of all the cards in these tests, being marginally faster than the 8-disk
array for the 3Ware parallel ATA controllers. Also the 3Ware-SATA read
speeds did not significantly improve when 8 disks were included in its array
as opposed to 4 (See Table A.4). The write speeds achieved are comparable
to the equivalent speeds achieved with the parallel cards, being only slightly
faster with a 4-disk array and slightly slower with an 8-disk array.
Figure A.6 shows a comparison of the maximum (vm.max-readahead
1200) read and write speeds achieved for the various controllers and RAID-5
configurations. Table A.4 shows detailed read and write speeds for 2 GB
transfers. The greatest overall read speeds (approximately 1300Mbit/s) were