RAMDISK(4D) Devices RAMDISK(4D)
NAME
ramdisk - RAM disk device driver
SYNOPSIS
ramdisk@0:disknameDESCRIPTION
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)
