[Lazarus] filesystem timing Linux vs Win

[Florian Klämpfl]

Am 27.11.2010 20:31, schrieb Mattias Gaertner:
> On Sat, 27 Nov 2010 20:14:38 +0100
> Florian Klämpfl <florian at freepascal.org> wrote:
> 
>> Am 27.11.2010 18:53, schrieb Henry Vermaak:
>>> Also, the features of the filesystems
>>> are so different, you can't even compare them.  fat and ntfs are stuck
>>> in the dark ages compared to ext*.
>>
>> Modern NTFS implementations have some really nice and advanced features
>> none of the ext* has: snapshoting (saves file server admins a lot of
>> time :)) and transactions. I guess especially snapshotting makes ntfs
>> slow: CoW semantics simply requires a lot of coping of files and
>> fragments probably the disc. I made a similiar experience with btrfs
>> (whsich has CoW semantics by default as well) on linux, working with fpc
>> on a btrfs partition made fpc really slow. I didn't test further by
>> turning off CoW for btrfs, but it might be reason.
> 
> Florian, the reading/writing of files seems to be ok under Windows. But
> the file access functions are much slower than under Linux (file exists,
> date, open, close).
> fpc already caches these attributes, but of course it has to read them
> every time it starts. It reads over 80 directories. Maybe
> someone can check how much time this costs under windows.

I checked these things some years ago but at this time this wasn't a
problem. As Sven already mentioned, the only real bottleneck on windows
is process startup time.

Besides turning off atime, another important things on windows are:
never ever fill a hard disk more than approx. 80%. Filling a partition
more than 87.5% will probably fragment the MFT and this makes a system
really slow.

But after the first compilation, this is void anyways, all files are in
the disk cache if the system has sufficient memory.

> 
> BTW, some file systems like zfs under Linux have snapshots too, 
> and the file access is still as fast as ext*.

Of course, it might depend on the FS where it has its weakness: recently
I unpacked gcc sources on an xfs partition: it took several minutes, on
ext3 this takes only a few seconds.