On 21/04/17 23:39, Sidney_Kotic wrote:
> Lots of stuff in another thread about file systems.
>
> I mentioned defragmentation.  There seems to be a lack of understanding
> about what it is.  Has zilch to do with the TOC.
>
> ----
> In the maintenance of file systems, defragmentation is a process that
> reduces the amount of fragmentation. It does this by physically
> organizing the contents of the mass storage device used to store files
> into the smallest number of contiguous regions (fragments). It also
> attempts to create larger regions of free space using compaction to
> impede the return of fragmentation. Some defragmentation utilities try
> to keep smaller files within a single directory together, as they are
> often accessed in sequence.
>
> Defragmentation is advantageous and relevant to file systems on
> electromechanical disk drives. The movement of the hard drive's
> read/write heads over different areas of the disk when accessing
> fragmented files is slower, compared to accessing the entire contents of
> a non-fragmented file sequentially without moving the read/write heads
> to seek other fragments.
> ----
> https://en.wikipedia.org/wiki/Defragmentation
>
> Way back in the stone-age things like this were important when you were
> concerned about seek time and how it impacted performance.

And is one of the reasons that Linux uses by and large file systems
designed with all this in mind that don't actually fragment files. And
massive file caching too, so that memory that isn't needed for anything
else is acting as a fast random access copy of bits of the disk that you
have used recently.


Of course these days with SSDS who gives a ****. The relationship
between a requested track/sector isn't anything like constant as wear
levelling algorithms rearrange the SSD on a routine basis anyway.

And there is no seek time.

--
If you tell a lie big enough and keep repeating it, people will
eventually come to believe it. The lie can be maintained only for such
time as the State can shield the people from the political, economic
and/or military consequences of the lie. It thus becomes vitally
important for the State to use all of its powers to repress dissent, for
the truth is the mortal enemy of the lie, and thus by extension, the
truth is the greatest enemy of the State.

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