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

Radim Blazek radim.blazek at gmail.com
Sun Apr 28 11:40:12 PDT 2013

I am working on #6448 QGIS issue - Extremely slow shapefile reading
over network. You can find my latest observations in

Long story short, OGR does not buffer I/O and Windows does not always
cache network files.

I have few questions for OGR developers:
1. Are there my OGR related notes in the issue comment correct?
2. Would it be possible to implement buffering in VSI?
3. Is it VSI cache (if VSI_CACHE_SIZE is set to some small number)
suitable to be used as buffer?
4. Would it be possible to implement buffering or to extend VSI cache
for writing (to allow editing)?
5. Have you considered to increase CHUNK_SIZE (currently 32768)? Where
does that size comes from? I saw that XP is using 32768 but from what
I have read, SMB1 block size limit was 64K but SMB2 should not have
that limit. E.g. gvSIG 2.0.0 is using via its BigByteBuffer2 class
block size 61440.


More information about the gdal-dev mailing list