I had noticed on the forums that I wasn't the only person who was having the CPU maxed out when large attachments were sent. It doesn't appear, at least on the forums, that the problem had been solved, so I will open it up for discussion here, for anybody who could provide some sort of insight into a solution. So here is what I found:
It appears that this issue may be related to transfer rate, or at the least transfer rate affects it. If someone sends a large attachment from outside of our LAN, which I'll assume not too many of our clients would be coming in at any more than current Cable Upstream speeds, the CPU usage will only jump to about 30% (even though that in itself is still high). Concurrent attachments will obviously increase that. I can handle about 3 large attachments concurrently at this speed before the CPU maxes out. Now, if someone sends through our LAN, namely via our webmail interface (SquirrelMail), it only takes one large attachment and the CPU maxes out. That is because due to the way SquirrelMail works [and i assume other webmail progs as well], when a user uploads a file through the browser it uploads it to the web server. Then once the send button is pressed it sends the file directly from our webserver to our ASSP server, which would basically transfer as fast as each machine could handle. I wonder if there is anyway to limit the transfer rate per connection to see if this is the actual problem. Merak, my mail server, only lets me limit transfer rate for the entire SMTP service, not on a per connection basis, so I can't do it at that stage. Might need to submit a feature request to Merak, but this doesn't solve any of my problems any time soon. I wonder if there is a way to do it at the ASSP layer. I guess theoretically I could setup a SMTP relay between ASSP and Merak that allows such limiting. I think postfix does this, but I'm not sure. I'd have to look into it. To provide some more solid evidence to my belief that it was the transfer rate causing the problems, I sent a really large message directly from my machine on our network through the ASSP server, and modified the bandwidth allocated for Outlook, via a bandwidth limiter program I use, and noted the changes in CPU usage on our ASSP machine. Here are those numbers: In all cases this was the only message going through the server at the time. 10kbps - 7% CPU 20kbps - 13% CPU 30kbps - 19% CPU 40kbps - 27% CPU 50kbps - 34% CPU 60kbps - 41% CPU 70kbps - 46% CPU 80kbps - 54% CPU 90kbps - 61% CPU 100kbps - 66% CPU 110kbps - 72% CPU 120kbps - 79% CPU 130kbps - 86% CPU With no bandwidth limitations (other than the connection itself), it maxed out at 100% CPU. Any thoughts on how to fix it now that the problem has been more closely identified? Thanks David S ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Assp-user mailing list Assp-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/assp-user
