Double your disk read performance in a single command

blockdev --setra 1024 /dev/sdb
(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt. You may be can test the speed disk with some large file in your system, before and after using this: time dd if=/tmp/disk.iso of=/dev/null bs=256k To know the value of block device parameter known as readahead. blockdev --getra /dev/sdb And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)
Sample Output
# Before test
$ blockdev --getra /dev/sdb
256
$ time dd if=/tmp/disk.iso of=/dev/null bs=256k
2549+1 records in
2549+1 records out
668360704 bytes (668 MB) copied, 6,84256 seconds, 97,7 MB/s

real    0m6.845s
user    0m0.004s
sys     0m0.865s

# After test
$ blockdev --setra 1024 /dev/sdb

$ time dd if=/tmp/disk.iso of=/dev/null bs=256k
2435+1 records in
2435+1 records out
638390272 bytes (638 MB) copied, 0,364251 seconds, 1,8 GB/s

real    0m0.370s
user    0m0.001s
sys     0m0.370s

2
By: starchox
2009-02-18 16:27:01

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hay q?a :D
quydo · 266 weeks and 6 days ago

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