Some systems support the creation of RAM disks. A RAM disk is a device made from system memory that looks like a small disk device. Often, the contents of a RAM disk are erased when the system is rebooted. RAM disks that are erased on reboot prevent VxVM from identifying physical disks. This is because information stored on the physical disks (now erased on reboot) is used to identify the disk.
nopriv devices have a special feature to support RAM disks: a volatile option which indicates to VxVM that the device contents do not survive reboots. Volatile devices receive special treatment on system startup. If a volume is mirrored, plexes made from volatile devices are always recovered by copying data from nonvolatile plexes.
To create a RAM disk with VxVM
# ramdiskadm -a ramdiskname size
# ln -s /dev/ramdisk/ramdiskname /dev/dsk/ramdiskname # ln -s /dev/rramdisk/rramdiskname /dev/rdsk/rramdiskname
# vxddladm addforeign blockpath=/dev/ramdiskname charpath=/dev/rramdiskname
# vxdisk scandisks # vxdisk define ramdiskname type=nopriv volatile len=size
# vxdg -g diskgroup adddisk ramdiskname
# vxassist -g diskgroup make volume size ramdiskname
Some RAM disks are used in situations where all volume contents are recreated after reboot. In these situations, you can force volumes formed from RAM disks to be started at reboot by using the following command:
# vxvol set startopts=norecov volume