I have just bought a Rosewill RSV-S5, I have installed 5x1,5Tb Western Digital Green disks in it. After that have I created a Raid5 on them all with the software that followed with the hardware.
Not the raid it self works fine, but it is SLOW, I can only obtain a maximum of 25 MB/s, and if SABnzbd+ is downloading with 5 MB/s is it having a hard time streaming a normal DIVX (700 mb) movie.
Is this normal or is there something wrong?
Edit: should be able to handle 3 Gbps = 384 megabytes / second
Edit 2: 
As you can see am I only downloading with 3,76 MB/s and I'm trying to watch V s02e08 (720p), but it is completely unwatchable, as I can see 30 sec, and the it buffers for 20 sec.
Edit: Other information there might be required
I'm running Windows Server 2008 R2, optimized for program performance. Windows is installed on a 60GB SSD. I have a 50 Mb/s internet connection and a 1 Gb/s LAN, all connected with Cat6 Ethernet cables. The MCE is using a Gigabyte EP35C-DS3R motherboard with 2 GB DDR2 ram. 
Edit 3: I have used chunk sizes for 128 KB
Edit 4: I found this on newegg 
  Pros: Enclosure for 5x2TB hard drive
  is fine. This is basically a rebranded
  San Digital TR5M-B product. For
  support Rosewill tells you to contact
  San Digital. No direct support from
  Silicon Image for the computer raid
  card.
  
  Cons: Includes computer Silicon Image
  3132 raid card, extremely slow raid 5
  write (our tests ~10MB/s). Compare to
  regular internal local drive write
  30-60MB/s. We basically dumped the
  Sil3132 card and replaced with High
  Point RocketRaid 622 card for extra
  $69.99. Note for RR622, turn off ECRC
  (end to end CRC check) for card to
  work on IBM xserver. What took 12hrs
  to copy now took 2-3hrs. San Digital
  realized the problem and has the newer
  model TR5M-BP TowerRaid Plus that
  comes with High Point RocketRaid 622
  card. Rosewill should discontinue this
  product and go with TR5M-BP. Could not
  get Silicon Image raid management
  software to work with complicated
  2008R2 server with 10 NICs,
  application doesn't know how to talk
  to localhost port with all those NICs.
  No updates from Silicon Image and
  support from San Digital ignored. Gave
  up on Sil3132 card. Save yourself from
  a lot of headaches, get the RR622 card
  too if you are going to buy this
  product.
  
  Other Thoughts: The newer model is
  TR5M-BP TowerRaid Plus, comes with
  High Point RocketRaid 622 raid card
  for the PC instead of Silicon Image
  Sil3132. According to San Digital,
  raid 5 performance for Sil3132 read
  80MB/s write 19MB/s, and RR622 read
  154MB/s write 149MB/s. Our RR622 tests
  gave (8TB raid 5) write ~80-110MB/s
  copying 40GB file took 8mins.
So I have now ordered a HighPoint RocketRAID 622 2P ext SATA III and hopes that it will solve my problems.