IBM LTO type M cartride (M8)
The LTO program introduced a new capability with LTO 8 tape drives: the ability to write 9 TB (native) on a brand new LTO Ultrium 7 cartridge instead of 6 TB (native) as specified by the LTO 7 format. Such a cartridge is called an LTO Type M cartridge. These cartridges are identifiable by using an automation barcode label ending with the characters M8.
Hereafter, these cartridges will be referred to as L8, M8, and L7, respectively.
Only new, unused LTO Ultrium 7 cartridges can be initialized as M8 cartridges. Once a cartridge is initialized as M8, it cannot be changed back to L7. Initialized M8 cartridges can only be written and read in an LTO 8 tape drive; LTO 7 tape drives cannot read initialized M8 cartridges.
M8 cartridges can be purchased as either pre-initialized (also referred to as “labeled and initialized”) M8 data cartridges or un-initialized M8 data cartridges (M8 WORM cartridges are not supported). For either option, the barcode label is included; however, the un-initialized M8 data cartridge must first be initialized in tape libraries that support the automatic initialization of un-initialized M8 cartridges while under the control of ISV applications that recognize the M8 barcode label.
A tape cartridge is initialized when it is first loaded into a compatible tape drive and data is written by the ISV application at the beginning of tape (sometimes referred to as “labeling a tape” or “writing from BOT”). The tape drive establishes the density of the media at that time.
If an un-initialized M8 cartridge is not initialized in a tape library that supports un-initialized M8 cartridges, then the cartridge may inadvertently and silently be initialized at the L7 density (i.e., at a 6 TB native capacity) even if the barcode label states M8. This could occur with the usage of non-TS4500 tape libraries, stand-alone LTO 7 tape drives, stand-alone LTO 8 tape drives, down-level LTO 8 tape drive firmware, down-level TS4500 tape library firmware, or down-level ISV software that does not recognize that M8 cartridges should only be mounted in LTO 8 tape drives. M8 cartridges that are inadvertently initialized at the L7 density can continue to be read and written in LTO 7 and LTO 8 tape drives; however, they will remain limited to the 6 TB native capacity.