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bug#10561: stat unclear about size on disk and type of blocks discussed

From: Filipus Klutiero
Subject: bug#10561: stat unclear about size on disk and type of blocks discussed
Date: Tue, 07 Feb 2012 13:26:21 -0500
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:8.0) Gecko/20120104 Icedove/8.0

Hi Pádraig,

On 2012-01-20 19:03, Pádraig Brady wrote:
On 01/20/2012 05:47 PM, Filipus Klutiero wrote:
Hi Pádraig and Jim,

On 2012-01-20 09:15, Pádraig Brady wrote:
On 01/20/2012 02:03 PM, Jim Meyering wrote:
Pádraig Brady wrote:
As for %o, if you'd ask me what "I/O block size" means without any
context, I'm far from being sure I would answer it means size on
disk. I suggest to call this Size on disk, or Size used on the
I/O implies transfer.
So it corresponds to an "optimal transfer size hint"
This value can be different at each layer, for example:

$ stat -c "%o" .                # file level
$ stat -f -c "%s" .             # file system level
# blockdev --getioopt /dev/sda  # device level

I'm not sure what language should be used instead. Perhaps instead
of blocks the manual should talk about "data storage device blocks".
I suppose we could clarify "I/O block size" a bit.
How about s|I/O block size|optimal I/O block transfer size|
or even without "block",

    "optimal I/O transfer size"
OK I'll go with "optimal I/O transfer size hint",
since there is nothing guaranteed about it,
and in fact it's often wrong.


I'm sorry but this change does not really address my concern.
It does actually, because...

The previous definition of %o did refer to "block" without specifying which kind of 
block. This is no longer the case as the new definition no longer refers to blocks. However, I 
still do not consider the new definition, "Optimal I/O transfer size hint", 
To come back to my original problem, I tried figuring out how much disk space a small file took. In Windows, 
I would look at "Size on disk". If "optimal I/O transfer size hint" means size on disk, 
this is still very unclear. Even after reading your answers, I don't understand what "Optimal I/O 
transfer size" means.
I am not looking for a transfer size.
... you know to ignore %o

What do you mean?

My question is, if I'm putting a small file on my filesystem, how much space 
will it use.
Here are 2 new descriptions I suggest:
Size occupied when including slack space
Size of the clusters occupied

Appart from %o, the ambiguity problem in the descriptions of %b and %B remains.
No it does not.

Really? The description of %b still reads:
Number of blocks allocated (see %B)
How does this description exclude that it refers to file system blocks?

As I said they're abstract entities only valid in relation to each other.
Just multiple %b x %B to get your answer.

If these statistics are internals, please mention that. It would also be nice to explain if the user can do anything with these internals.
You may have missed the start of the last mail, where I said
the du command is more appropriate (it does the above for you).

I did not miss that. I was looking for information from stat. I am not asking stat to provide that information. What annoyed me was that I couldn't tell if stat was providing that information because some of the statistics displayed were unclear. I'll try to remember to use du for that, thanks, but it's easier to remember a single command, and I generally prefer a command that tells me both the size on disk and the actual size.

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