On Jan 5, 2009, at 9:44 AM, D Stubbs wrote:
>
>
> It's a 'Stack of Disks'
> >
> > If it is a stack of discs (platter)- and if something failed does
> > it stand to reason that it would fail one disc at at time?
>
> BUT ---- Data is written on all of the #1 cylinders (tracks on the
> disk), then writing moves to 'Cylinder #2', then Cylinder #3,.........
>
> > - so one's best security is to perhaps partition exactly to each
> disc?
> So Partitions do NOT correspond to 'disks' (platter)
> >
> I am trying to get my head around this concept - that a partition
> is not a partition.
Think this way ----
Hard disk = File cabinet
Indexing system for locating data within the file cabinet = APS,
FAT32, FAT16 etc.
the top level of designations may be referred to as Partitions (or
not) Its all treated the same the same as 'File Names'.
Within 'Partitions' you have 'File Names' & 'Directories' [Remember
being told that 'Directories are just a 'special case file name'?]
Partitions are just another 'Special Case' of 'File Name'.
To help visualize how the HD organizes things, you can think of
partitions as drawers in the file cabinet. [But that's to help you,
NOT an actual representation of real life.]
So, we have HD, partition table (tree), directories (more sub-trees)
& files (data), directories (more sub-trees) & files (data) ...
Meanwhile, the HD subsystem has been putting data of varying types
here and there on the sectors available. (Starts out as a nice clean
'Start at sector #1, next, next" situation', then, the nice one right
after the other pattern 'goes to hell, in a handbasket' [Deleting
things, returns their 'used sectors' to the 'free sector' list ----
at the end of the list, and in whatever order they came available.
I.E. "Use next sector" could be anyplace on the HD.]
Notice, nowhere in this 'write data' description, is there a
reference to Partition, Directory, or File Name. The HD doesn't care,
all it does is keep track of where to find the NEXT sector used by
this 'batch of DATA' (directory, file).
This is why 'Crashes' can be so disastrous.
{Crash -- In the olden days, referred to what was usually an actual
'crash' of the read/write head onto the surface of the 'platter/ drum
(real old tech). Today is usually just a glitch on the surface of the
platter that doesn't respond properly to write/ read commands
(something that can develop over a period of time.)}
Said 'crash' confuses the electronics. It can no longer locate the
'Next' place to write/ read.
This is where 'Disk Recovery Software' goes to work, it ignores the
'original' tree structure, and reads everything, and tries to fit the
pieces back together (Often quite successfully).
This description is NOT a 'super accurate definition', its a
generalized tale of what is probably happening.
Specific Manufacturers do their own thing sometimes 'inside the HD'.
[Makes life interesting for the Data Recovery folk.]
Chuck D.
> Tried googling "Understanding Partitions" and "What is a
> Partition". All I found were basic descriptions of the fact. Even
> found a recent blog by Dan Knight on his partitioning:
> http://lowendmac.com/musings/08mm/partition-your-hard-drive.html
> But I am no further in understanding what is actually happening.
> I suppose it is some kind of 'virtual directory'?
> What makes no sense yet to me is how, say partition #3 could go
> bad, and not the others - if it they all bunched together.
> But then this question may be beyond the scope of the present
> discussion - maybe someone knows of a url that is 'Understanding
> partitions 101 for the average idget'?
> Thanks for all the help, I have decided on 3 partitions.
> Del
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