With the Network Services Server option “Maximize Throughput for Network Applications” enabled, using the NTFS and its associated cache can improve Sybase IQ database performance for both inserts and queries. This is largely due to the NTFS being able to store significantly more data than the Sybase IQ buffer cache with the same amount of physical memory. This advantage can be most effectively be leveraged by reducing the size of the main cache, giving this memory to the NTFS which can use it more effectively. In IQ 15.x more use is made of temporary caches in load and query processing. As a result, using the NTFS cache is still a useful technique for the main cache, but may not provide the same advantages for the temporary cache.
The Sybase IQ buffer caches store Sybase IQ data (pages) in uncompressed form. As a result, a Sybase IQ buffer cache of 100MB can store 100MB worth of data. Conversely, the NTFS cache manages Sybase IQ data in its compressed form. Therefore, if the compression ratio were 2:1, 100MB of NTFS cache is potentially storing 200MB of Sybase IQ data. As a result, the NTFS cache is likely to sustain a higher cache hit rate which can lead to a reduction in I/O. The savings in I/O outweigh the computational overhead needed to decompress data as it moves from the NTFS cache to the Sybase IQ buffer caches.
