Re: Aligning file system data

[Robert Hancock <hancockr@shaw.ca>]

John Richard Moser wrote:
> How likely is it that I can actually align stuff to 31.5KiB on the
> physical disk, i.e. have each block be a track?

I don't think this is very likely. Even being able to find out what the 
physical disk arrangement is, or whether it is consistent in terms of 
track size, etc. seems unlikely.

> Rather than leveraging the track cache, would it be less expensive for
> me to simply read in blocks totaling about 16 or 32KiB all at once?

For block sizes that small I think that the kernel should be smart 
enough to do this itself, there is no need to concern with such low 
level details in the application.

> How much more latency is involved in (B) than in (C)?  Does crossing a
> track boundary incur anything expensive?

Given that both the disk and the kernel will likely read far more than 
32KB ahead I can't see much difference other than the overhead inside 
your application..

--
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

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