This weekend, the error message “device or resource busy” almost drove me crazy when I was trying to assemble (activate) a software RAID array.

I was experimenting with a software RAID-1 setup (two mirrored disks) using VirtualBox before planning to deploy it to a live server. Because I never liked the idea of creating 4 partitions on each disk and mirror them with individual arrays (/dev/md0 to /dev/md3), I planned to create one partitionable array that spans the whole disks (/dev/md_d0). I.e. the one and only array /dev/md_d0 consists of two whole disks /dev/sda and /dev/sdb. The advantage: the second drive is an exact copy of the first one – even partition table and master boot record are identically – just like with a hardware RAID. So in emergency cases, you can even use one of the disks directly, without activating RAID drivers.

I encountered a really odd phenomenon with syslog-ng yesterday. A mail- and web-server with considerable traffic was disconnected from the net for some hours during a router failure. After the router came back online and the server was reachable again, I noticed an unusual high system CPU load. Strangely, the server itself wasn’t changed in any way (it wasn’t even shut down) and suddenly the CPU utilization raised to around 80%, whereas it normally stays under 20%. Strange thing was, that most CPU time seemed to be eaten up by the syslog-ng daemon.