IO performance test with tuning (reset readahead)

Here are some IO performance (we focus on the tow IO patterns :read and write)test with tuning of the readahead attribute of block devices.

we use "blockdev" to set different ra(readahead) attribute of the device,such as:

blockdev --setra  /dev/sdc

we use "iozone" to test the IO performance after the tuning,such as

/usr/local/bin/iozone -Rab /atlas/data16/iotest/iozone/iora_result_d128 -s 15g -y 32k -q 8192k -i 0 -i 1
 

parameters for IOZONE:

-a run a automatic model
-R generate excel output file
-b output in excel worksheet file
-s set the file size to test
-y set minimum record size
-q set maximum record size
-i o read model
-i 1 write model

umfs01

the X coordinate represents the record size of read or write. Its UNIT is MB

the Y coordinate represents the IO rate according to different record size and different RA size.

Lines of different color represtents different RA(readahead) size. its number means how many blocks (each block is 512MB). 128 means the readahead size is 128*512MB.

The file size we tested on umfs01 is 15G

Read Performace on UMFS01

Write Performace on UMFS01

umfs03

the X coordinate represents the record size of read or write. Its UNIT is MB

the Y coordinate represents the IO rate according to different record size and different RA size.

Lines of different color represtents different RA(readahead) size. its number means how many blocks (each block is 512MB). 128 means the readahead size is 128*512MB.

The file size we tested on umfs03 is 15G

Read Performace on UMFS03

Write Performace on UMFS03

umfs05

the X coordinate represents the record size of read or write. Its UNIT is MB

the Y coordinate represents the IO rate according to different record size and different RA size.

Lines of different color represtents different RA(readahead) size. its number means how many blocks (each block is 512MB). 128 means the readahead size is 128*512MB.

The file size we tested on umfs01 is 15G

Read Performace on UMFS05

Write Performace on UMFS05

conclusions:

RA has an important influence on the read rate of disk. In general ,the read rate can increase with the increasement of RA size, but to a certain value, it can reach to a peak read rate,then the read rate descend with the increasement of RA size. RA size also has an influence on the write rate(the same trend as Read rate), but not as obvious as the read rate..

-- WenjingWu - 28 Sep 2007