Note that we didn&#x27;t run stock freebsd. It was a custom freebsd4 with a custom gcc 2.95 toolchain. I don&#x27;t remember all the mods, but migrating from 4 to 6 was a nice undertaking, and it was done in parts. People who worked there will remember the term &quot;4 on 6&quot;. After the migration, the kernel was 6 (and you got the latest drivers) but we were still running those weird 4 user-land binaries.<p>Inktomi (YST) was acquired in 2003, later Overture (YSM) and both were linux shops. YST was the biggest property by far and we didn&#x27;t have any kernel developers. We were doing just fine with stock debian, then stock RHEL. (I did a few very minor patches for 32-bit, like splitting user-space&#x2F;kernel to 3.5&#x2F;0.5G instead of 3&#x2F;1G, and some caching improvements for &#x2F;proc, but I wasn&#x27;t a kernel developer). Linux just worked. Drivers were available and supported for the HW we needed. Oprofile, systemtap worked fine for the most part. We later hired one kernel developer to help Mail move to linux, but we always had more freebsd kernel developers.<p>For freebsd you needed to write the drivers and the tools. That took time and money. The community was also smaller and it was harder to hire people with experience. Acquisitions were running on linux too.<p>The decision was not easy. Y! already had <i>great</i> freebsd engineers. By announcing that linux would be the supported platform going forward it was a given that many of them wouldn&#x27;t be happy and leave. Fortunately not all of them left. For example Peter W. still works there.<p>In any case I don&#x27;t think there was really an alternative.