dd if=/dev/zero of=/root/testfile bs=1G count=1 oflag=direct
Raid O
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 4.63741 s, 232 MB/s
SSD Raid0
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 2.60729 s, 412 MB/s
Raid 5
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 2.8916 s, 371 MB/s
Then, with the cache deactivated (hdparm -W0 /dev/sda):
dd if=/dev/zero of=/root/testfile bs=1G count=1 oflag=direct
Raid 0
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 3.73241 s, 288 MB/s
Raid 5
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 2.44875 s, 438 MB/s
SSD Raid0
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 1.21236 s, 886 MB/s
In this test, 512 bytes were written one thousand times, first with the cache activated (hdparm -W1 /dev/sda):
dd if=/dev/zero of=/root/testfile bs=512 count=1000 oflag=direct
Raid 0
1000+0 records in
1000+0 records out
512000 bytes (512 kB) copied, 0.0609285 s, 8.4 MB/s
Raid 5
1000+0 records in
1000+0 records out
512000 bytes (512 kB) copied, 0.0532276 s, 9.6 MB/s
SSD Raid 0
1000+0 records in
1000+0 records out
512000 bytes (512 kB) copied, 0.0603067 s, 8.5 MB/s
hdparm -tT /dev/sdax
Raid0
Timing cached reads: 24104 MB in 2.00 seconds = 12063.16 MB/sec
Timing buffered disk reads: 812 MB in 3.00 seconds = 270.23 MB/sec
SSD Raid 0
Timing cached reads: 21946 MB in 2.00 seconds = 10983.56 MB/sec
Timing buffered disk reads: 2514 MB in 3.00 seconds = 837.71 MB/sec
Raid 5
Timing cached reads: 26560 MB in 2.00 seconds = 13293.19 MB/sec
Timing buffered disk reads: 732 MB in 3.00 seconds = 243.99 MB/sec
Voila où j'en suis