| From: | Xavier Messersmith |
| Date: | 13 Aug 2000 at 06:46:07 |
| Subject: | Re: PFS and AmigaOS 3.5 |
On 12-Aug-00, xbj@lvdi.net wrote:
> What I'm wondering is, just exactly why is
> Amiga's FFS so slow,
Is it a pile of fecal matter inferior to the filesystem used by Commodore 64
computers. Whats there to wonder?
> and what do they consider
> the disk validation process so important?
And why do they?
When a filesystem is rendered invalid, there may be files that point to other
files, directories inside themselves, and a whole bunch of other more
insideous asynchronocities lurking about. If anything is written based on
those wrong bits of data more stuff can go wrong.
> Doesn't data reliability suffer when the disk
> status isn't constantly checked and updated?
It doesn't need to be constantly checked and updated, it isn't going anywhere.
It just has to keep everything in sync at the time of writing, and everything
should be well.
> I'm guessing that FFS writes the directory
> information last while the others write it first.
Its a bit more complex than that. The main problem is the block layout of the
Fast File System. It takes a block to do about anything. All those blocks must
all be in agreement. With PFS and SFS they put alot more data into the blocks,
one block can now point to the existance of several files and the affected
blocks don't have to be put into effect until all the changes are made.
Less to write, better organization, speedier file accesses, less chance to
screw up.
>>>> Here are Amiga Format's filesystem test results in seconds:
>>>> Copy Rename Delete
>>>>
>>>> FFS 254.72 103.04 7.74
>>>> PFS3 35.04 4.16 2.64
>>>> SFS 54.36 5.32 8.46
Awwww, poor SFS deletes slower than FFS. :-)