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
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
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