[gdal-dev] OGR slow with network files on Windows

[Radim Blazek]

On Mon, Apr 29, 2013 at 10:55 AM, Even Rouault
<even.rouault at mines-paris.org> wrote:
> Selon Radim Blazek <radim.blazek at gmail.com>:
>
>> On Mon, Apr 29, 2013 at 10:23 AM, Even Rouault
>> <even.rouault at mines-paris.org> wrote:
>> > I'm also wondering if setting unconditionnaly VSI_CACHE might not have some
>> > theoretical penalty for fast access storage when there is a lot of seeking
>> and
>> > reading by small amounts (I believe this is the typical I/O pattern when
>> you
>> > display a JPEG2000). It might be relevant to have an option to enable
>> > caching/buffering for files only located on SMB folders.
>>
>> How do you recognize if a file is SMB?
>
> I was wondering that too and hoped you would known the answer ;-) There's
> perhaps a Windows API for that... ?

There seems to be: GetVolumePathName + GetDriveType which should be
DRIVE_REMOTE.
maybe also PathIsNetworkPath.

It seems to me that VSI cache as buffer (small VSI_CACHE_SIZE) should
always be used on Windows by default with network files. It should go
to OGR, I think.

Radim

> FWIK SMB filenames are in the form "servershared_folderxxxx" , but it can be
> mounted on a drive, so it becomes "X:shared_folderxxxx". Perhaps there's a way
> of resolving this to the original name ?
>
> But I'm not sure it is really needed either. Perhaps the theoretical performance
> loss is neglectable in practice. I'm just throwing thoughts.
>