Limit hard drive i/o usage by one process (Dropbox)

I'm using only 5% of 1TB given by Dropbox and it regularly chokes my Mac Mini's HDD by "Downloading file list" too often.

I think it's just a poor performance (it started since the last Dropbox version) but Dropbox support does not understand the problem. So I would like to limit reading and writing by the process.

Is it possible? (OS X 10.9)

UID    PID   PPID CMD              DEVICE  MAJ MIN D   %I/O
0      0        0 kernel_task      ??        1   4 W      0
501  67690    164 Google Chrome    ??        1   4 W      0
501  83207  67690 Google Chrome H  ??        1   4 W      0
501  83194    164 mdworker         ??        1   4 R      0
501  67690    164 Google Chrome    ??        1   4 R      0
501  83207  67690 Google Chrome H  ??        1   4 R      3
501  83071    164 Dropbox109       ??        1   4 R     93