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Showing posts from October, 2011

More fun with the LSI MegaRAID controllers

As I mentioned in a previous post, we've had some issues with the LSI MegaRAID controllers on our Dell C2100 database servers. Previously we noticed periodical slow-downs of the databases related to decreased I/O throughput. It turned out it was the LSI RAID battery going through its relearning cycle.

Last night we got paged again by increased load on one of the Dell C2100s. The load average went up to 25, when typically it's between 1 and 2. It turns out one of the drives in the RAID10 array managed by the LSI controller was going bad. You would think the RAID array would be OK even with a bad drive, but the drive didn't go completely offline, so the controller was busy servicing it and failing. This had the effect of decreasing the I/O throughput on the server, and making our database slow.

For my own reference, and hopefully for others out there, here's what we did to troubleshoot the issue. We used the MegaCli utilities (see this post for how to install them).

Check…

Good email sending practices

I'm not going to call these 'best practices' but I hope they'll be useful if you're looking for ways to improve your email sending capabilities so as to maximize the odds that a message intended for a given recipient actually reaches that recipient's inbox.

Make sure your mail servers are not configured as open relaysThis should go without saying, but it should still be your #1 concernUse ACLs and only allow relaying from the IPs of your application serversCheck your servers by using a mail relay testing serviceMake sure you have reverse DNS entries for the IP addresses you're sending mail fromThis is another one of the oldies but goldies that you should double-checkUse DKIMFrom the Wikipedia entry: DomainKeys Identified Mail (DKIM) is a method for associating a domain name to an email message, thereby allowing a person, role, or organization to claim some responsibility for the message. The association is set up by means of a digital signature which can be…