FYI - This turned out to be a couple of different problems.
1. Of the 14 DNS blacklists I was using, 4 of them were routinely slow, even to the point of timing out. I ditched them.
2. The iMail drive had 45% file fragmentation. I had thought that this wouldn't be an issue, because in our system, the iMail data files are blown away every week (we insert them into a database in real-time). Boy, was I wrong on that one. Even after a weekly deletion, the file fragmentation was this in the 40s. Running a defrag solved it (8 hours later), and I added the defrag to our weekly downtime batch.
After taking these steps, we got the lag down from 30-60 seconds to 2-3 seconds. Each step appeared to account for about half of the slowdown.
Thanks!
-Chase
Chase Seibert | Network and Systems Engineer | Bullhorn Inc. | 617.464.2440 x119 | www.bullhorn.com
-----Original Message-----
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED];
Sent: Oct 5, 2004 10:36:45 AM
Subject: DNS Blacklist Speed
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED];
Sent: Oct 5, 2004 10:36:45 AM
Subject: DNS Blacklist Speed
We are seeing a slight 30-60 second delay on incomming email, which I've tracked down to the DNS blacklist lookups. I have a couple of questions regarding how to fix this, if possible. Granted, I do have 14 rules, which I suppose I could cut back on.
1. Why aren't these queries done in parallel? Could they be? I suspect this would speed them up by a factor of 10.
2. Is 14 rules too many, or do I just have to live with a 30 delay at this number?
3. Would caching speed this up? I have the iMail DNS cache set to 200. Does this get used for blacklists? Should I up it?
4. Has anyone implimented some kind of caching on their local DNS server that would speed this up? We run MS DNS, not sure what the caching is like.
I know a 30-60 second delay is not that bad; email is not IM after all. However, prior to having spam filtering, it was virtually instantaneous (1-2 seconds). The clients are givin us a hard time about it, even though they love the spam filtering.
Thanks!
-Chase
Chase Seibert | Network and Systems Engineer | Bullhorn Inc. | 617.464.2440 x119 | www.bullhorn.com
