What is next to 48 LBA ?

[vdumitru85]

What is next to 48 LBA ?

48-bit Logical Block Addressing
Logical block addressing (LBA) is a common scheme used for specifying the location of blocks of data stored on computer storage devices, generally secondary storage systems such as hard disks. 48-bit LBA allows a motherboard or add-in hard disk controller to address more than 137GB of data. A 48-bit controller will address up to 2 Terabytes of data.

 

[Paperdoc]

I'm guessing you're wondering how we go beyond 2 TB HDD's, which are now common. Don't worry. The explanation of 48-bit LBA you quoted is wrong by a big factor, because it throws in a different limit not caused by the 48-bit LBA design.

The original LBA system used a 28-bit binary address, so up to 2^28 sectors on a HDD could be addressed. Until recently, the common design put 512 bytes into one sector. So 2^28 sectors, times 512 bytes per sector, yields a max size of 137,438,953,472 bytes, or 137.4 GB if you define "GB" to be 1,000,000,000 bytes.

The new system uses a 48-bit binary address instead. So the maximum number of sectors is now 2^20 times that original max, and that's 1,048,576 times - roughly one million 137 GB units in ONE storage device! I doubt we'll ever get there with rotating platter hard drives.

Despite that potential, current software designs (notably in the Partition Table and File System structures) limit the max size of a single bootable Partition in Windows to 2 TB. Other OS's or other Partition systems can go larger than that in a bootable volume. I'm not exactly sure how large for current systems, but until we get a lot bigger than 3 TB it won't matter. But again, that's a limit that can be changed as a new OS and File system is designed and deployed in time for very much larger storage devices.