sraw(8) [debian man page]

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 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)

RAW(8)							       System Administration							    RAW(8)

NAME

       raw - bind a Linux raw character device

SYNOPSIS

       raw /dev/raw/raw<N> <major> <minor>

       raw /dev/raw/raw<N> /dev/<blockdev>

       raw -q /dev/raw/raw<N>

       raw -qa

DESCRIPTION

       raw  is	used  to  bind	a  Linux raw character device to a block device.  Any block device may be used: at the time of binding, the device
       driver does not even have to be accessible (it may be loaded on demand as a kernel module later).

       raw is used in two modes: it either sets raw device bindings, or it queries existing bindings.  When setting a raw device,  /dev/raw/raw<N>
       is  the	device name of an existing raw device node in the filesystem.  The block device to which it is to be bound can be specified either
       in terms of its major and minor device numbers, or as a path name /dev/<blockdev> to an existing block device file.

       The bindings already in existence can be queried with the -q option, which is used either with a raw device  filename  to  query  that  one
       device, or with the -a option to query all bound raw devices.

       Unbinding can be done by specifying major and minor 0.

       Once  bound  to	a block device, a raw device can be opened, read and written, just like the block device it is bound to.  However, the raw
       device does not behave exactly like the block device.  In particular, access to the raw device bypasses the  kernel's  block  buffer  cache
       entirely:  all I/O is done directly to and from the address space of the process performing the I/O.  If the underlying block device driver
       can support DMA, then no data copying at all is required to complete the I/O.

       Because raw I/O involves direct hardware access to a process's memory, a few extra restrictions must be observed.  All I/Os  must  be  cor-
       rectly  aligned	in  memory  and on disk: they must start at a sector offset on disk, they must be an exact number of sectors long, and the
       data buffer in virtual memory must also be aligned to a multiple of the sector size.  The sector size is 512 bytes for most devices.

OPTIONS

       -q     Set query mode.  raw will query an existing binding instead of setting a new one.

       -a     With -q , specify that all bound raw devices should be queried.

       -h     Provide a usage summary.

BUGS

       The Linux dd(1) command should be used without the bs= option, or the blocksize needs to be a multiple of the sector  size  of  the  device
       (512 bytes usually), otherwise it will fail with "Invalid Argument" messages (EINVAL).

       Raw  I/O devices do not maintain cache coherency with the Linux block device buffer cache.  If you use raw I/O to overwrite data already in
       the buffer cache, the buffer cache will no longer correspond to the contents of the actual storage device underneath.  This is  deliberate,
       but is regarded either a bug or a feature depending on who you ask!

AUTHOR

       Stephen Tweedie (sct@redhat.com)

AVAILABILITY

       The raw command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							    August 1999 							    RAW(8)