RAMDISK(7D)RAMDISK(7D)NAMEramdisk - 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 buf‐
fer. A single read or write call usually results in a single I/O oper‐
ation, 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(5) for descriptions of the following attribute:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Evolving │
└────────────────────┴─────────────────┘
SEE ALSOramdiskadm(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. Accord‐
ingly, use ramdisks only when absolutely necessary.
Mar 04, 2003 RAMDISK(7D)
