cvmkfile(1)                                                        cvmkfile(1)

NAME

       cvmkfile - Create a pre-allocated file

SYNOPSIS

       cvmkfile [-k <key>] [-p] [-s] [-w] [-z] <size>[k|m|g] <filename>

DESCRIPTION

       cvmkfile  can  be used to pre-allocate a file on the Xsan volume.  This
       is useful and preferable when preparing a file for use in  a  real-time
       or  streaming environment as the entire file is represented in only one
       file system extent. Additionally, a file can be placed onto a  specific
       storage pool by specifying the <key> value, which is used as the affin-
       ity locator. See cvfs_config(4) for more details about affinities.

USAGE

       The -k <key> optionally tells the file system where to place  the  data
       file.   If  an Affinity Key is specified, the file is placed on storage
       pools that are specified to support this key. If there  is  no  storage
       pool  with  the key specified, then the file is placed in non-exclusive
       data pools. If there are no non-exclusive data pools, then  ENOSPC  (no
       space) is returned.

       The -p option forces the allocation and any subsequent expansions to be
       fitted "perfectly" as multiples  of  the  InodeExpandMin  configuration
       parameter.  The  allocation extent will always line up on and be a per-
       fect multiple of the blocks specified in InodeExpandMin.

       The -s option forces the allocation to line up on the  beginning  block
       modulus  of  the  storage pool. This can help performance in situations
       where the I/O size perfectly spans the  width  of  the  storage  pool's
       disks.

       The  -w  option  sets the file size to be equal to <size>. Without this
       option the blocks are allocated but the size  is  set  to  zero.  NOTE:
       Unless the -z option is used, the new file will contain undefined data.
       Using the -w option is not recommended unless absolutely needed.

       The -z option causes the file to be physically  zeroed  out.  This  can
       take a significant amount of time.

       The  <size>  argument  specifies  the  number  of  bytes, kilobytes(k),
       megabytes(m) or gigabytes(g) to allocate for the  file.   There  is  no
       guarantee  that  all  requested  space  will be allocated.  If there is
       insufficient contiguous available space to satisfy the requested amount
       then  a  "best effort" will be performed.  In this case a success value
       is returned even though not all of the requested amount is allocated to
       the  file.   Even  though the allocation may not be fully satisfied, if
       the -w option is specified then the file size will  still  reflect  the
       requested <size> value.

EXAMPLES

       Make  a file of one gigabyte with zero length. Allocate it on a storage
       pool that favors the media type 6100_n8.

          rock # cvmkfile -k 6100_n8 1g foobar

SEE ALSO

       cvfs_config(4), cvmkdir(1)

Xsan File System                 December 2005                     cvmkfile(1)