Am Samstag, den 01.03.2008, 12:48 -0600 schrieb Matt: [...] > Hardware is: > AMD64 Dualcore 3800+ just updated to 5600+ > 4Gbyte DDR2 > SATA2 500GB drive > > Normally load average is like 8 or less but at peak times I am seeing > it spike to like 100 area. Upgrading the CPU gained very little. I > am thinking I am disk I/O bottle necked. I have about 2000 email > accounts and according to eximstats at peak times I am seeing > "Messages received per hour" of 40K. Actually, so far you failed to state a problem. Load is something like "number of processes waiting to be processed" and I have seen servers with load-values higher thann 1000 which still reacted faster than my laptop.
Load is not a problem. It might indicate a problem, but load itself is only a symptom. Disk-IO might be an explanation for "high" load-values. There are countless others. Find the real one before desperatly trying out possible solutions... when I read your questions and the first answers which all circled around "optimising disk-io by tuning the kernel" I just felt desperation. Nobody even considered wheater or not your asumptions sound reasonable. Nobody even asked questions.... First, 2000 email-accounts does not sound like a big deal, the number of messages does. But of course, that's just 20 messages/mailbox. You mention one harddisk and that you can't afford a long downtime. That worries me. You can't provide reliable service without decent storage (raid 1 or raid5, and backup, of course) and regular maintenance. Fix that. In order to understand the real problem, you need data about your system. For example, recent top (I prefer atop) with recent kernel will show a value "wa" which is short for waiting. If you really have a problem regarding disk-io, "wa" should show this. Cpu(s): 1.4%us, 0.5%sy, 0.0%ni, 98.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st I highly recommend running "munin" on every exim-server. It will gather lots of numbers regarding your server, which can be invaluable when facing problems. In my experience the most likely cause for high load-values on exim-serves is DNS-related. If you process 40k messages an hour and use SpamAssassin, more than 500k DNS-requests are likely. If you didn't worry about a local caching-DNS-daemon on your mailserver, than you should do that now. If you already have a local caching-DNS-daemon on your mailserver, consider moving it to a different server. Any further advice would be wild guessing, so it's up to you to provide further data. -- CU, Patrick.
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