For SATA and SAS Disk Drive with 512bytes logical block size:
LBA counts = (97,696,368) + (1,953,504 * (Advertised Capacity in GBytes – 50))
Or
Advertised Capacity (GB) = [(LBA counts – 97,696,368)/1,953,504] + 50
Numbers 97,696,368, 1,953,504 and 50 are constants.
The lower 3 bits of the LBA count are zero (divisable by 8 with a remainder of 0). This is in order to provide a even number of aligned sectors for emulation.
Examples:
To advertise a 500GB capacity, the required LBA count is:
LBA count = 97696368 + (1953504 * (500 – 50)) = 976,773,168
If a drive has a 585,397,500 LBA count then the advertised capacity is:
Advertised Capacity = [(585,397,500 – 97,696,368)/1,953,504] + 50 = 300GB
NOTE: Drives less than these capacity points may not comply with this document:2.5” SATA 80GB, 3.5” SATA 160GB, 2.5”/3.5” SAS 450GB.
For SATA and SAS Disk Drives with a logical block size of 4096 bytes:
The formula is scaled by dividing the first two constants by eight. This results in consistent capacity margin over the basic capacity.
LBA counts = (12,212,046) + (244,188 * (Advertised Capacity in GBytes – 50))
Or
Advertised Capacity (GB) = [(LBA counts – 12,212,046)/244,188] + 50
Examples:
To advertise a 500GB capacity (LDS format), the required LBA count is:
LBA count = 12,212,046 + (244,188 * (500 – 50)) = 122,096,646
If a LDS drive has a 109,887,246 LBA count, then the advertised capacity is:
Advertised Capacity = [(109,887,246 – 12,212,046)/244,188] + 50 = 450GB
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