ramdisk(7D)

NAME

     ramdisk - RAM disk device driver

SYNOPSIS

     ramdisk@0:diskname

DESCRIPTION

     The ramdisk driver supports numerous  ramdisk  devices  that
     are  created  by  the  system  during the boot  process (see
     boot(1M))   or   during   normal   system   operation   (see
     ramdiskadm(1M) for more information).

DEVICE SPECIAL FILES

     Each ramdisk can be accessed either as a block device or  as
     a  raw  device.  When accessed as a block device, the normal
     buffering          mechanism is used when reading  from  and
     writing  to  the  device,  without  regard  to physical disk
     records. Accessing the  ramdisk  as  a  raw  device  enables
     direct  transmission  between the disk and the read or write
     buffer. A single read or write call  usually  results  in  a
     single   I/O  operation,  meaning that raw I/O is more effi-
     cient when many bytes are  transmitted. You can  find  block
     files  names  in  /dev/ramdisk.  Raw file names are found in
     /dev/rramdisk.

     There  are  no  alignment  or  length  restrictions  on  I/O
     requests to either block or character devices.

ERRORS

     EFAULT
           The argument features a bad address.

     EINVAL
           Invalid argument. EIO. An I/O error occurred.

     EPERM Cannot create or delete a ramdisk without  write  per-
           mission on /dev/ramdiskctl.

     ENOTTY
           The device does not support the requested ioctl  func-
           tion.

     ENXIO The device did not exist during opening.

     EBUSY Cannot exclusively open /dev/ramdiskctl. One  or  more
           ramdisks are still open.

     EEXIST
           A ramdisk with the indicated name already exists.

     EAGAIN
           Cannot allocate resource for ramdisk. Try again later.

FILES

     /dev/ramdisk/diskname
           Block device for ramdisk named diskname.

     /dev/rramdisk/diskname
           Raw device for ramdisk name diskname

     /kernel/drv/ramdisk
           32-bit driver

     /kernel/drv/ramdisk.conf
           Driver configuration file. (Do not alter).

     /kernel/drv/sparcv9/ramdisk
           64-bit driver

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     bute:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Evolving                    |
    |_____________________________|_____________________________|

SEE ALSO

     ramdiskadm(1M), fsck(1M), fstyp(1M),  mount(1M),  newfs(1M),
     driver.conf(4), filesystem(5), dkio(7I)

NOTES

     The percentage of available  physical  memory  that  can  be
     allocated   to  ramdisks  is  constrained  by  the  variable
     rd_percent_physmem.  You  can  tune  the  rd_percent_physmem
     variable  in  /etc/system.  By  default,  the  percentage of
     available physical memory that can be allocated to  ramdisks
     is fixed at 25%.

     A ramdisk may not be the best possible use of system memory.
     Accordingly, use ramdisks only when absolutely necessary.