Greetings,
We have several classic ASP apps that we have developed. We recently
upgraded two servers that these apps run on to Win2K3/IIS6. They were
previously running W2K/IIS5.
We use ASP sessions to store session state in memory. Like others who
have this setup, we had to alter worker process recycling, etc in order
to preserve this session state. After following the advice in numerous
posts and some experimentation, we had disabled worker process
recycling, had no memory limits and no idle limits set. Still, while
watching ASP/Sessions Current with perfmon, we'd see sessions drop from
1500 or so down to 0 and then start climbing back up. The interval
appeared to be pretty random. Sometimes, it'd be twice within a 5
minute period. Sometimes, it'd be an hour or more. We turned on
logging via the metabase, but no events ever showed up in the event
log.
We moved the sites to their own application pools, which limited the
damage when one site would fail, but provided no further insight into
the issue.
As a last ditch effort, we changed the servers to use IIS 5 isolation
mode. Now, the behavior is different. It happens on both servers at
19 minutes past the hour (most hours). Sometimes, it will skip an
hour, but when it does happen, it's at that time. Sometimes it happens
on one server and not the other.
We've disabled Antivirus in case scanning was causing IIS to think
files like global.asa had changed. DLLHost.exe consumes about 400MB
physical memory most of the time when the app's running at full zoot.
Other misc details:
- No other scheduled tasks that run at that time.
- Haven't found anything obviously traffic related in the IIS logfiles,
but this is pretty difficult to identify. There are no indications
that IIS restarts, nor any IIS related errors in there.
- Still no entries in the System or Application even logs.
- Noticed in perfmon logs that at the time that the sessions drop off,
there are 12 or so Engine Flush Notifications that appear right after
that, if that has any significance.
Hardware:
Intel dual core processors
4 GB RAM
Any insight or similar experience out there? Is there any process
recycling mechanism that is still in play when running in IIS 5
isolation mode?
Thanks in advance,
Greg