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       sraw - benchmark raw scsi I/O performance under linux


       sraw [ -fiv6 ] scsi-device [ bstart [ bstep ] ]


       This program basically reads the specified scsi device and measures the
       throughput.  Note that  the  filesystem  *AND*  the  buffer  cache  are
       bypassed by this code, this program was designed to benchmark the naked
       scsi drivers by themselves without the need to account for the overhead
       of  any other portion of the kernel. It also could be used to benchmark
       disk read throughput.

       This program does a series of reads of the disk, of  consecutive  areas
       on  the disk.  The device is first queried to determine the sector size
       for the device, and then the series of reads is begun.  About 5.0 Mb is
       read  from  the  device, and then the performance numbers are reported.
       Note that since the buffer cache is completely bypassed,  there  is  no
       need to be concerned about cache hits or anything.

       Output  of  sraw  is  a  set  of  lines, 4 numbers per line: blocksize,
       elapsed time, nblocks and throughput (in bytes per second).

       scsi-device is either a block device (e.g. /dev/sda,  /dev/scd0)  or  a
       generic SCSI device (e.g. /dev/sg0).


       -f     set  FUA  (Force Unit Access) bit during read. Data is then read
              from media instead of internal drive cache.

       -i     use legacy ioctl instead of new SG I/O layer (will not  work  on
              2.6 kernel and block devices).

       -v     more verbose output.

       -6     use 6-bytes instead of 10-bytes read command. In this case, only
              the first GB of data could be read from media.

       bstart starting block to check different zones on ZBR discs

       bstep  factor for sequential stepping, default 1.  Use  0  for  reading
              always the same blocks (from cache)


       sraw  could  issue  input/output errors when reading too many blocks at
       the same time from a block device like /dev/sda. To get  rid  of  them,
       use /dev/sgN instead.


       sraw  was  first written by Eric Youngdale.  Extensions (-v, -f, -6, SG
       IO, man page) were written by Eric Delaunay.


       sg_dd(8) from sg3-utils package.


       sraw is available at

                                   Nov 1993