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Full Discussion: Disk read and write speed.
Special Forums Hardware Filesystems, Disks and Memory Disk read and write speed. Post 302445778 by Corona688 on Tuesday 17th of August 2010 12:24:13 AM
Old 08-17-2010
That will be inaccurate because of cache... stuff written to disk just gets shoved into memory until the disk's ready. 30 gigs would probably fill the cache, but still, there's better ways that don't involve waiting for 30 gigs of data to be written.

Linux usually has the hdparm command. It has read tests that take just a few seconds:
Code:
hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   1582 MB in  2.00 seconds = 791.21 MB/sec
 Timing buffered disk reads:  184 MB in  3.04 seconds =  60.61 MB/sec

There's no equivalent write-speed test but, for a traditional hard disk, read speed and write speed should be about the same.
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dskx(8) 						      System Manager's Manual							   dskx(8)

Name
       dskx - generic disk exerciser

Syntax
       /usr/field/dskx [ options ] -rdev
       /usr/field/dskx [ options ] -pdevpart
       /usr/field/dskx [ options ] -cdev

Description
       The exerciser tests the disk drives on your system.  The exerciser has three main options which include read only, write/read/validate data
       on a partition, and write/read/validate data of a disk.

       The exerciser does random seeks and reads of random block sizes and random seeks, writes, reads, and validations of random data patterns of
       random block sizes. The exerciser will run until or kill -15 pid is sent to the process.

       A  logfile is made in for you to examine and then remove. If there are errors in the logfile, make sure you check the file, because that is
       where the driver and kernel error messages are saved.

       CAUTION: Both the -c and -p options of the exerciser destroy data on the disk.  Use extreme caution before using them  on  any  non-scratch
       media.  If you are unsure of what data is on the disk, contact your system manager before running with either of these options.

Arguments
       One of the following function flags and arguments must be specified.

       -rdev	 Performs a random read-only test on all partitions except the c partition.  The dev argument can be a raw or buffered device name
		 and number.  For example, rhp0, ra3, hk1.

       -pdevpart Writes, reads, and validates data from the device name and number specified by dev and the partition specified by part.  The  dev
		 argument  can be a raw or buffered device name and number.  For example, rhp0, ra3, hk1.  The part argument can be any valid par-
		 tition from a - h.

		 CAUTION:  Be careful when exercising partitions that overlap other partitions, as you may inadvertently destroy data on a  parti-
		 tion that you do not want to test.  You can use the -q option of the command to see what partitions overlap on the device on your
		 system.

       -cdev	 Writes, reads, and validates data from all partitions except the c partition on the device specified by dev.	The  dev  argument
		 can be a raw or buffered device name and number.  For example, rhp0, ra3, hk1.

Options
       The options are:

       -h	 Prints help message for the command.

       -ofile	 Saves output diagnostics in file.

       -tn	 Specifies the run time in minutes (n).  The default is to run until the process receives a or kill -15 pid.

       -dm	 Prints statistics every m minutes.

Restrictions
       If  there  is  a  need to run a system exerciser over an NFS link or on a diskless system there are some restrictions.  For exercisers that
       need to write into a file system, such as the target file system must be writable by root.  Also the directory, in which any of	the  exer-
       cisers  are  executed,  must be writable by root because temporary files are written into the current directory.  These latter restrictions
       are sometimes difficult to overcome because often NFS file systems are mounted in a way that prevents root from writing into them.  Some of
       the restrictions may be overcome by copying the exerciser to another directory and then executing it.

Examples
       The following example exercises RA disk unit 1, for 60 minutes in the background:
       % /usr/field/dskx -t60 -cra1 &
       The following example exercises raw HP disk unit 0, partition d, until or kill -15 pid:
       % /usr/field/dskx -prhp0d

See Also
       Guide to System Exercisers

																	   dskx(8)
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