Quote:
I've seen NTFS fragment terribly when only 50% full.
Me too.
After a cleanup of a full 40 Gb NTFS drive down to 60% full I've had the M$ Windows XP defrag take 30 hours despite having 2 Gb memory fitted. After that the system ran normally.
Similarly a large unix UFS /tmp mounted partition which briefly contained 400,000 files and directories (after a programming accident) ran really slowly afterwards until re-created from scratch.
With large database systems pre-allocating the segments means that you do not have disc fragmentation but that the database engine needs to handle fragmentation.
I've seen databases left to expand dynamically which caused severe slow running due to disc fragmentation even though the database engine reported no fragmentation. A database dump/load to preallocated segments on a properly tuned filesystem cured the problem.
09-06-2010
