Thin Provisioning; Logical Block Provisioning; Thin Provisioning Capabilities; Unmap - Seagate ST400FM0323 Product Manual

3.8

Thin Provisioning

3.8.1

Logical Block Provisioning

The drive is designed with a feature called Thin Provisioning. Thin Provisioning is a technique which does not require Logical Blocks
to be associated to Physical Blocks on the storage medium until such a time as needed. The use of Thin Provisioning is a major factor
in SSD products because it reduces the amount of wear leveling and garbage collection that must be performed. The result is an
increase in the products endurance. For more details on Logical Block Provisioning and Thin Provisioning, Reference the SBC-3
document provided by the T-10 committee.
3.8.2

Thin Provisioning capabilities

The level of Thin Provisioning support may vary by product model. Devices that support Thin Provisioning are allowed to return a
default data pattern for read requests made to Logical Blocks that have not been mapped to Physical Blocks by a previous WRITE
command.
In order to determine if Thin Provisioning is supported and what features of it are implemented requires the system to send a READ
CAPACITY 16 (9Eh) command to the drive. Thin Provisioning and the READ CAPACITY 16 (9Eh) command is defined in the Seagate
SCSI Command Reference 100293068.
Product Configuration
Non-SED
SED
A logical block provisioning management enabled (LBPME) bit set to one indicates that the logical unit implements logical block
provisioning management. An LBPME bit set to zero indicates that the logical unit is fully provisioned and does not implement
logical block provisioning management.
A logical block provisioning read zeros (LBPRZ) bit set to one indicates that, for an unmapped LBA specified by a read operation, the
device server sends user data with all bits set to zero to the data-in buffer. An LBPRZ bit set to zero indicates that, for an unmapped
LBA specified by a read operation, the device server may send user data with all bits set to any value to the data-in buffer.
3.8.3

UNMAP

The UNMAP command requests that the device server break the association of a specific Logical Block address from a Physical Block,
thereby freeing up the Physical Block from use and no longer requiring it to contain user data. An unmapped block will respond to a
READ command with data that is determined by the setting of the LBPRZ bit in the READ CAPACITY parameter data.
3.8.4

FORMAT UNIT command

A device which supports Thin Provisioning will be capable of performing a SCSI FORMAT UNIT command which allocates Logical
Blocks Addresses that are not linked to Physical Block Locations. A FORMAT command will cause all LBAs to become unmapped.
Seagate 1200.2 SAS SSD Product Manual, Rev. A
LBPME
Supported
Supported
LBPRZ
Supported
Not Supported
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