Changing the reported capacity of disk drive
Disk devices that speak the SCSI protocol (SCSI, SAS, Fibre channel, and even USB memory sticks) have a built-in command designed to specify the drive capacity. The block size and count is defined as mode page settings, so any software product that incorporates a mode page editor has the mechanism to allow you to change the capacity (or block size) of a device.
Why you might want to do this …
- You have some older equipment running an operating system such as VMS, or certain RAID controllers that have an upper limit on the maximum disk size which they support.
- You want to be really sneaky and hide information on a disk drive. (Once you resize the disk, the “hidden” area is hidden from everything, including low-level formats, partition managers, and anti virus software).
- You are trying to mirror disk drives, and while they are both advertised to be 146GB large, they have a slightly different number of total blocks. As such, some RAID software won’t let you mirror the two drives.
Security warning — If you do not want to risk data theft, you should always insure that the disks in your storage farm report 100% of their actual capacity before running software to view the contents, or run a secure erase.
Use smartmon-ux -capacity n <drivelist> to set reported number of blocks
- Reformatting is not necessary after changing capacity. Data is preserved once you restore the hidden area.
- Even USB flash memory capacity can be changed with smartmon-ux, so you could add two partitions on a USB stick, hide stuff in the 2nd partition, then change capacity as needed to make the partition invisible.
- smartmon-ux -capacity 0 resizes the disk to factory default, and exposes all hidden areas to insure that somebody isn’t trying to hide anything.
- More details on usage at http://www.santools.com/smart/unix/manual