disk recovery

A hard disk recovery partition is a method used to store recovery information on a personal computer. Many OEM manufacturers use the recovery partition to store a complete copy of the hard disk's factory default contents for easy restoration. For more details on the process of hard disk restoration, see Recovery CD.

Methods

• Most manufacturers include a *hidden partition* on the disk which contains a filesystem containing recovery software and disk images. When the user invokes the recovery method, the system hides the active system partition and unhides the recovery partition, allowing it to boot. The recovery software will re-hide its own partition after creating a new partition and installing software to it.
• A more dangerous approach is to simply leave a certain section of disk unallocated in the partition table and store a filesystem there. While this can prevent operating systems such as Linux from easily accessing the data, it also means the data could be easily overwritten if any partitioning tools were to be used on the disk. This method requires some BIOS involvement to "temporarily" assign the free space to a partition.
• Some systems, most notably IBM systems, use a method known as the Pre-Desktop Area. This method is similar to the first method listed here, however the BIOS participates in the process, effectively changing the reported size of the hard disk to the system. For example, if the hard disk is 40GB in size, and there is a hidden recovery partition of 4GB, the system will see the drive as a 36GB drive. Basically, the reported disk geometry is altered so that the recovery partition is completely inaccessible to the system. This approach could potentially cause some issues with running operating systems such as Linux which can sense discrepancies between the BIOS and the hardware.
• A very few manufacturers will simply create a second partition and assign it to a drive letter. On that partition is the recovery software. This was typically done on older systems where a boot floppy was used to initiate the recovery process.

Advantages

A hard disk recovery partition presents the following advantages

• Convenience - no CD or DVD to keep track of, and quick access to the recovery usually through a keystroke pressed during startup
• Speed - in some cases reading the recovery data from a hard disk may be faster than from a CD or DVD. This may be negated, however, by the fact that the data is being both read and written to the same physical disk.
• Lower cost - It is asserted that not needing to press, label, and package recovery CDs can reduce the cost of manufacturing on OEM systems.

Disadvantages

• Reliability - The hard disk recovery partition does no good if the hard disk fails. With a CD or DVD, a user can install a new hard disk and then run the recovery CD to install the bundled software. Some manufacturers offer CD versions of the recovery software for a fee, however this can be inconvenient in an emergency.
• Flexibility - Upgrading a hard disk becomes a challenge. Since there frequently is no actual setup CDs for the various software programs included on the system, a user may be forced to purchase imaging software to transfer the installation from the original hard disk to a newer, larger one, since the user is unable to install everything from scratch, as is sometimes recommended when installing a new drive. This also means the recovery partition will no longer be usable on the new disk.
• Loss of disk space - Placing the recovery data on the hard disk means that a certain amount of disk space is not available for use by the user. On modern systems this can be on the order of several gigabytes.
• Danger of damage - Many methods of partitioning are susceptible to damage. If tools such as Partition Magic or Parted are used on the disk, the recovery partition could be easily damaged, deleted, or altered. Since a CD is a fixed medium that cannot be erased, it could be stated that the CD is more reliable than the hard disk method.