I''m trying to track down a performance problem that has suddenly appeared on my Bacula server that runs as a VM. The performance hit comes when Bacula starts inserting values into mysql temp tables. strace tells me that the calls go like: write (512 bytes) fsync() write(1024 bytes) fsync() ... And each fsync call takes between 100ms and 200ms to complete, limiting the inserts to 5-10 per second. All the backup IO takes place on another physical server so it''s only the mysql throughput that is limiting me here. iostat -x tells me that %iowait is at 100% on the DomU, and around 75% on each of the physical RAID1 disks on the Dom0, with throughput being <100kbytes/second. I''m using Debian 3.8.x kernels from experimental, but the problem existed with the Debian 3.2 kernel from wheezy too. This setup has been running fine and then suddenly started doing this. dd with oflag=direct gives me the expected performance in both dom0 (~90mbytes/second) and domu (~80mbytes/second), so I think the disks themselves are good. smartctl says both physical drives are health and there is no other performance problem on the system. I''m running out of things to point the finger at... any suggestions greatly appreciated! Thanks James