RAMDISK(4D) RAMDISK(4D)

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(8)) or during normal system
operation (see ramdiskadm(8) 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 efficient 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 permission on
/dev/ramdiskctl.


ENOTTY
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.


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(7) for descriptions of the following attribute:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Evolving |
+--------------------+-----------------+

SEE ALSO

dkio(4I), driver.conf(5), filesystem(7), fsck(8), fstyp(8), mount(8),
newfs(8), ramdiskadm(8)

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.


March 4, 2003 RAMDISK(4D)