Transfer Rate Disk


 
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# 1  
Old 03-14-2011
Transfer Rate Disk

hi guys

I have a linux server which has about 5 volumes from SAN (fiber channel) now I need to measure the transfer rate between one LUN which is a Logical Volume to another LUN which is another Logical Volume.

so basically this server has 5 LUNs from SAN
each SAN volume is a logical volume presented to linux

any tool to measure transfers rate (Megabytes per second)

so while I copy a file like 1 Terabyte I can get MB/second

thanks a lot
# 2  
Old 03-14-2011
Since this is Linux, if you send a SIGUSR1 to dd while it's in operation, it will print statistics to standard error.
Code:
# useless:  read /dev/zero, write /dev/null, in blocks of one megabyte
$ dd if=/dev/zero of=/dev/null bs=1048576 &
[1] 25076
$ killall -USR1 dd
4115+1 records in
4115+0 records out
4314890240 bytes (4.3 GB) copied, 2.38339 s, 1.8 GB/s
$ killall dd
[1]+  Terminated              dd if=/dev/zero of=/dev/null bs=1048576
$

It will also print a summary to standard error when it completes.

You may want to add "oflag=sync" to prevent cache effects from messing up your numbers.
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# 3  
Old 03-14-2011
i have to take a closer look since I did not get the idea just reading it Smilie

Quote:
Originally Posted by Corona688
Since this is Linux, if you send a SIGUSR1 to dd while it's in operation, it will print statistics to standard error.
Code:
# useless:  read /dev/zero, write /dev/null, in blocks of one megabyte
$ dd if=/dev/zero of=/dev/null bs=1048576 &
[1] 25076
$ killall -USR1 dd
4115+1 records in
4115+0 records out
4314890240 bytes (4.3 GB) copied, 2.38339 s, 1.8 GB/s
$ killall dd
[1]+  Terminated              dd if=/dev/zero of=/dev/null bs=1048576
$

It will also print a summary to standard error when it completes.

You may want to add "oflag=sync" to prevent cache effects from messing up your numbers.
# 4  
Old 03-17-2011
dd is a general purpose data moving command. It's sometimes used for moving data from one raw disk to another but it's a flexible command and doesn't care what kind of files or devices it's talking to.

dd by itself just reads stdin and writes back to stdout, so dd < filename > newfile is effectively the same thing as cp.

It does it in blocks of 512 bytes by default, which is a bit inefficient, so dd bs=1048576 < filename > newfile may be much faster. Beyond a certain point making the buffer bigger doesn't help.

So all I'm doing is having dd read from one file and write to another, and while it's running, sending it the signal SIGUSR1 which casues it to print statistics. Or you could wait for it to end, or kill it with ctrl-C, and it'll print statistics as it ends.

cache effects are when the OS doesn't immediately store what you've written to file on disk, just in memory. This is great for programs since they don't have to wait for the disk to catch up but troublesome for benchmarks. dd in linux supports the oflag=sync option to tell it not to do that.
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