clamd using 100% on database reloading. normal?

I frequently notice clamd taking up 100% CPU and increasing the server load a few times per day for about 20 mins each time. So I investigated and noticed that this is happening every time clamd reloads its signature database.

e.g. sample log from /var/log/clamd/clamd.log

Tue Apr 22 07:19:50 2008 -> SelfCheck: Database modification detected. Forcing reload.
Tue Apr 22 07:19:50 2008 -> Reading databases from /var/clamav
Tue Apr 22 07:37:37 2008 -> Database correctly reloaded (266939 signatures)

As you can see, the process of reading the database takes 20 minutes. During this 20 minutes the server load spikes up from 0.5 to 2+

Is this normal? Can someone check their /var/log/clamd/clamd.log and tell me if it takes this long on their servers as well?

Thanks.