User manual

WebPAM User Manual
100
The Expansion feature applies only to RAID 0 and RAID 5 arrays. You can add
physical drives as described in the table below.
Ranges of Logical Drive Expansion
There are limitations to how large you can expand a logical drive, depending on
the size of your current logical drive.
The current PC Operating Systems support a 10-byte LBA format. This means
that a logical drive can have up to 4 billion address blocks or sectors.
Multiply the number of blocks by the sector size to find the capacity of a logical
drive:
4,000,000,000 blocks x 512 bytes per sector = 2,048,000,000,000 bytes
of data for a 2TB drive.
Note that you cannot change the size of the sectors nor can you increase the
number of address blocks above 4 billion.
As a result, there are range limits imposed upon logical drive expansion as
shown in the table above. For example:
• You can expand a 2.5 TB logical drive up to 4 TB
• You can only expand a 1.9 TB logical drive up to 2 TB
From To Result
RAID 0: 1 drive RAID 0: 2, 3 or 4 drives Increased capacity
RAID 0: 2 drives RAID 0: 3 or 4 drives Increased capacity
RAID 0: 3 drives RAID 0: 4 drives Increased capacity
RAID 5: 3 drives RAID 5: 4 drives Increased capacity
Important
• The Target logical drive may require more disk drives than the
Source logical drive
• If the Target logical drive requires an EVEN number of disk
drives but the Source logical drive has an ODD number, ADD
a disk drive as part of the migration process
• You cannot reduce the number of disk drives in your logical
drive
• You cannot migrate or expand a logical drive when it is Critical
or performing activities such as Synchronizing or Rebuilding