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Alan McKinnon wrote: |
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>>>> dd if=/dev/sda2 of=/dev/null |
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>>>> 957169664 bytes (957 MB) copied, 17.5531 s, 54.5 MB/s |
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>>>> dd if=/dev/sda12 of=/dev/null |
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>>>> 820854784 bytes (821 MB) copied, 21.4136 s, 38.3 MB/s |
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>>> What do you conclude from this? |
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>> I'd say that /dev/sda2 is near "beginning" of disk (outer side, |
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>> more sectors per cylinder, higher transfer speed), and /dev/sda12 |
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>> is near "end" of disk (inner side, less sectors per cylinder, |
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>> lower transfer speed). |
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> |
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> Ah, I see my troll caught one already. You seem to be under the common |
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> delusion that the structure reported by fdisk actually means something about |
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> the physical disk :-) |
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Correct me if I'm wrong, but I do not remember saying anything like |
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that. And frankly, I can not image how you came to that conclusion. |
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I just said /dev/sda2 is probably on the outer side, and /dev/sda12 |
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on inner side, based on that difference in transfer speeds... |
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|
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> These days the entire concept of a "cylinder" is a mere abstraction to make |
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> tools like fdisk work in a sane manner. |
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|
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Partially correct. True is, C/H/S numbers in fdisk does not have any |
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practical meaning these days. But there are still cylinders, heads |
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and sectors on disk. And total number of sectors reported by fdisk |
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is the same, as real total number of sectors on disk. These sectors |
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are numbered starting first with the most outer tracks on disk on |
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all physical cylinders, continuing towards the inner most track. |
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This holds true for nearly all sata/pata-disks. Maybe scsi/sas |
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have different sector numbering scheme... |
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|
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> But yes, it does seem that in this case sda2 is probably near the outer edge |
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> of the platter where the head speed relative to the disk is higher. |
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Well, I'd say head speed does not anything to do with it. What makes |
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transfer rate on the outer tracks of disk faster is higher number of |
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sectors per cylinder, because nowadays disks have about constant |
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"bit-density" (only "about" constant, because number of sectors |
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per cylinder is a discrete number)... |
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|
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Jarry |
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-- |
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