The output
Timing cache reads: 184 MB in 2.03 seconds = 90.64 MB/sec
Timing buffered disk reads: 32 MB in 3.10 seconds = 10.06 MB/sec
Hmm..your disk speed is slow compared to mine and mine are not the fastest.
Are you running endian on one harddisk only?
How much time does the AV take to start?
That depends on your machine but it should not take long at all. It looks to me that it's only few seconds.
But disk I/O is increased during the running of it.
Could you post the output of top?
Are you running out of RAM? If swap is used machines usually go down to a crawl speed.