sraw(8) - man - phpman

SRAW(8)                                System Manager's Manual                               SRAW(8)



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  de‐
       signed  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 de‐
       vice 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)