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).
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.
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.
Block device for ramdisk named diskname.
Raw device for ramdisk name diskname
Driver configuration file. (Do not alter).
See attributes(5) for descriptions of the following attribute:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
ramdiskadm(1M), fsck(1M), fstyp(1M), mount(1M), newfs(1M), driver.conf(4), filesystem(5), dkio(7I)
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.