Saturday, February 10, 2018

linux - Understanding fdisk -l output and calculating storage

I have basic understanding of disk. (Please correct me if i am wrong) I understand on 1 platter, there are 2 heads, 1 on top, and 1 on bottom. Both side of the platter is able to provide storage ? On the platter, there are many tracks being broken up into the smallest unit of storage = sector. Corresponding tracks across all the platters = cylinder.


In OS, a block/cluster can be 1 or more sector


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This is my output of fdisk -l



Disk /dev/sda: 107.4 GB, 107374182400 bytes


255 heads, 63 sectors/track, 13054 cylinders


Units = cylinders of 16065 * 512 = 8225280 bytes


Sector size (logical/physical): 512 bytes / 512 bytes


I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk identifier: 0x0000d866



From the output, can i say that there are


q1) is there a total of 13054 tracks per platter then ? since there are 13054 cylinders ?


q2) there are 2 sides to a platter, does a track or sector applies to 1 side
of a platter or both sides ?
(e.g. if there is 1 track on platter, does it literally means 2 track, 1 on top and 1 below ?)


q3) what does the UNITS calculation represent ?
Why isn't the total storage in a disk =
no. of platter (not sure if top and bottom counts) * no of tracks per platter * no of sector per track * size of sector ?


q4) What does 255 heads means ?


Noob

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