So following my recent blog post on SANSlide WAN optimization appliances for use with Storwize replication, IBM has just announced Storwize 7.2 (available December) which includes not only replication natively over IP networks (licensed as Global Mirror/Metro Mirror) but also has SANslide WAN optimization built-in for free. i.e. to get the benefits of WAN optimization you no longer need to purchase Riverbed or Cisco WAAS or SANSlide appliances.
Admittedly, Global Mirror was a little behind the times in getting to a native IP implementation, but having got there, the developers obviously decided they wanted to do it in style and take the lead in this space, by offering a more optimized WAN replication experience than any of our competitors.
The industry problem with TCP/IP latency is the time it takes to acknowledge that your packets have arrived at the other end. You can’t send the next set of packets until you get that acknowledgement back. So on a high latency network you end up spending a lot of your time waiting, which means you can’t take proper advantage of the available bandwidth. Effective bandwidth usage can sometimes be reduced to only 20% of the actual bandwidth you are paying for.
The first time I heard this story was actually back in the mid-90’s from a telco network engineer. His presentation was entitled something like “How latency can steal your bandwidth”.
SANSlide mitigates latency by virtualising the pipe with many connections. While one connection is waiting for the ACK another is sending data. Using many connections, the pipe can often be filled more than 95%.
If you have existing FCIP routers you don’t need to rush out and switch over to IP replication with SANSlide, especially if your latency is reasonably low, but if you do have a high latency network it would be worth discussing your options with your local IBM Storwize expert. It might depend on the sophistication of your installed FCIP routers. Brocade for example suggests that the IBM SAN06B-R is pretty good at WAN optimization. So the graph below does not necessarily apply to all FCIP routers.
When you next compare long distance IBM Storwize replication to our competitors’ offerings, you might want to ask them to include the cost of WAN optimization appliances to get a full apples for apples comparison, or you might want to take into account that with IBM Storwize you will probably need a lot less bandwidth to achieve the same RPO.
Even when others do include products like Riverbed appliances with their offerings, SANSlide still has the advantage of being completely data-agnostic, so it doesn’t get confused or slow down when transmitting encrypted or compressed data like most other WAN optimization appliances do.
Free embedded SANSlide is only one of the cool new things in the IBM Storwize world. The folks in Hursley have been very busy. Check out Barry Whyte’s blog entry and the IBM Storwize product page if you haven’t done so already.