Promise Technology FastTrak TX4310 User Manual page 114

FastTrak TX4310 User Manual
Ranges of Disk Array 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 billiion.
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
See the table below.
• 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, even if the Target logical drive requires fewer disk
drives than the Source logical drive
• RAID 1 (mirror) works with two disk drives only
• You cannot migrate a logical drive when it is Critical or
performing activities such as Synchronizing, Rebuilding and
PDM
• RAID level migration is not possible to or from JBOD
Important
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