Heavy I/O blocks FreeBSD box for several seconds

[arrowdodger]

2011/7/6 O. Hartmann <ohartman at zedat.fu-berlin.de>

> When performing an update on the ports tree via "portsnap fetch update" or
> when checking out (or) large Subversion repositories or when copying large
> data files (~ 50 to 250 GB in size, results from numerical modelings) or
> when compiling world, FreeBD 9.0 and FreeBSD 8.2-STABLE tend to "freeze" for
> several seconds or drop overall performance dramatically for seconds. On
> boxes with only console- or terminal access (no GUI) a running 'vi' gets
> stuck for seconds while one of the processes producing heavy I/O is running,
> or the output of a 'cat' of a large file stops for several seconds.
>
> Using X11, this phenomenon gets even worse and the 'freezing' tends to
> persist sometimes for more than 10 or 15 seconds.
>

I've also had (and still having) this problem on FreeBSD 7.2-RELEASE and
8-STABLE with both UFS and ZFS. Though, i've been running FreeBSD not on
powerful servers, but on laptops (2-core CPU's, 2 GB of RAM). But still,
KDE4 on Linux performs much better during high disk IO.