Linux, OpenBSD, Windows Server Comparison: OpenBSD Stability and Reliability

Both my Windows NT and Linux web servers kept basically the same system install from the spring of 2000 to the summer of 2001. A few minor system changes have been made on both. In contrast my OpenBSD web server has been upgraded twice and my firewall three times following new version releases (2.7, 2.8 and 2.9). These were not simple standard installs or upgrades. Each was a new install working towards a highly customized, hardened system as documented in my large section Hardening OpenBSD Internet Servers. These systems have all had custom kernels. All operating systems require rebooting to replace the kernel so there is no way to compare the OpenBSD reboots to the other systems which have never been customized to any significant degree. Some of the OpenBSD systems have been deliberately stripped and rebuilt to test system recovery procedures. After I've finished experimenting with an OpenBSD system and put it into production use as a web server or firewall, OpenBSD stability seems comparable to Linux.

Everything I know and read about OpenBSD tells me it should be more stable than any version of Linux. My personal observations suggest otherwise. Theoretically, I have to acknowledge that my custom kernels could be responsible for any observed instability. If I were adding custom components, turning on advanced features or modifying any functions this would be likely. As I am only trying to turn off every capability not actually needed by my systems, it seems unlikely. When I've turned off something I needed, the effect has usually been immediate and obvious, such as the CD ROM drive or all networking functions not working at all.

I have notes on what appears to be an OpenBSD hard crash. (I maintain a log book in which I try to keep a record of significant system events.) During a large (> 200MB) FTP transfer, I deleted a huge directory structure (a complete UNIX system image) from the receiving FTP server placing a large I/O and CPU load on the FTP server. The client OpenBSD system locked up. I could not use any local console or existing telnet session and could not start a new telnet session. The kernel was not dead as it would still respond to pings but I had to reset the system to get it back.

Interestingly, my next note made the same day was the NT workstation experienced a total lockup. Unfortunately, I did not write the time down for these notes nor do the notes suggest any connection. I have no recollection how close the timing was so I don't know if there was a connection or just weird coincidence that two generally stable, completely different systems crashed on the same day. The NT workstation was not involved with the FTP transfer in any way. I don't normally document simple Windows lockups or crashes so I may have believed them related but if so, failed to put it in writing.

I have another note on OpenBSD networking failing during an FTP transfer. On this one an "sh ./netstart" was apparently sufficient to restore the networking functions.

It's also my recollection that the OpenBSD firewall experienced two hard crashes in the first six months it was in use but can find no record of these. I may be confusing these with incidents on which I do have notes. In two cases I lost connectivity to the Internet. I never had a clear diagnosis and in both at some point I rebooted the firewall but this did not fix the problem in either case. The notes suggest that a loose or bumped cable may have been the actual cause. I do have notes on a recent networking failure on the OpenBSD firewall. The bridge stopped forwarding packets between the inside and outside. A simple "#route flush; #sh /etc/netstart" fixed the problem in about 5 minutes.

I have no recollection of or notes on an OpenBSD web server ever crashing.

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