Need help with exam question.. transferring data from a track (HDD)

[XA04]

Hi guys. Got an exam tomorrow so just doing a bit of revision, but I don't seem to be able to figure this question out:

A 500 GByte hard disc drive consists of 5 double sided discs. Each
disc has 30 tracks and the disc drive has the following parameters:
Rotational Speed 7,200 rpm
Average seek time 8.5 ms
Transfer rate 120 Mbytes/s
Estimate the time taken to transfer 1MByte of data from a track
allowing for head movement and latency. [3 marks]

Looked on google, looked in my books.. can't really seem to find a solution of how you would calculate this. Surely it can't be too hard for 3 marks.. any help?

Thanks,
Adrian

[XA04]

Thank god.. it didn't come up in the exam anyway!

[Funkstar]

1/120 of a second + 8.5ms?

Surely the guff about 5 platters and 3 tracks is irrelevant?

[DavidM]

Depends how fragmented the data is.

[Funkstar]

That isn't specified or mentioned, so it's not something you can take into account.

[DavidM]

Although it's certainly a factor in real cases... (as I've found in the past)

[Funkstar]

oh for sure. just not something you can calculate with the data given.

[mac124]

1/120 of a second + 8.5ms?

Surely the guff about 5 platters and 3 tracks is irrelevant?

Looks like the logical answer to me

[circuitmonkey]

How much fragmentation can you really have on a 1 MB file?

[DavidM]

Every other sector on a different platter?

That could make a considerable difference

[circuitmonkey]

yes but with the most common block size being what... 512bytes, and I should think it would be unusual for the FS not to be able to find 2 contiguous blocks, anyway, i'm being argumentative.

[Johnakajohn]

In addition to the 8.5ms seek time and the 1/120 of a second to transfer the data you need to add 60 / 7200 of a second to allow for the possibility that the start of the data you want to read on the track just passed before the head moved into position.