It seems like Microsoft changed the way the memory manager works in the
new Windows 7 kernel (which is what Windows 2008 R2 uses), not letting
the system cache grows to use up all available RAM any more. (at least
not in a predictable manner)
Here's a reference: http://support.microsoft.com/kb/976618
"The memory management algorithms were updated to address this
problem in Windows 7 and Windows Server 2008 R2 operating systems.
Therefore, we do not recommend that you use the provided functions
or the Microsoft Windows Dynamic Cache Service in computers that are
running Windows 7 or Windows Server 2008 R2."
This is in some circumstances a good thing, but it also means that
things like Lucene now need to access the hard drive more than before.
We're storing a lucene index on an iSCSI SAN, which used to work great
pre W2K8 R2 because it eventually found its way into the system cache,
and it wouldn't hit the network any more. This doesn't happen any more
with R2 and we see some query time degradation.
The solution to this issue would be to use Memory Mapped I/O, but I see
that MMapDirectory is not implemented, are there any plans to implement it?
There is first class support for Memory Mapped Files in .NET 4.0 which
is still some time away, but until then the Win32 API could be used.
