Devices                                               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.

ERORS
     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
               permission on /dev/ramdiskctl.


     ENOTY    The device does not support  the  requested  ioctl
               function.


     ENXIO     The device did not exist during opening.


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





SunOS 5.11          Last change: 04 Mar 2003                    1






Devices                                               ramdisk(7D)



     EXIST    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


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



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Evolving                    
    


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

NOTES




SunOS 5.11          Last change: 04 Mar 2003                    2






Devices                                               ramdisk(7D)



     The percentage of available  physical  memory  that  can  be
     allocated   to  ramdisks  is  constrained  by  the  variable
     rdpercentphysmem.  You  can  tune  the  rdpercentphysmem
     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.













































SunOS 5.11          Last change: 04 Mar 2003                    3