NAME

       sraw - benchmark raw scsi I/O performance under linux

SYNOPSIS

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

DESCRIPTION

       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).

OPTIONS

       -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)

ERRORS

       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.

AUTHOR

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

SEE ALSO

       sg_dd(8) from sg3-utils package.

AVAILABILITY

       sraw is available at
       ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/

                                             Nov 1993                                     SRAW(8)