Hyperswap - IBM Storwize V5010 Manual

For those fabrics with 64 or more host ports, this recommendation becomes a rule. Therefore,
you see four paths to each volume discovered on the host because each host needs to have
at least two FC ports from separate HBA cards, each in a separate fabric. On each fabric,
each host FC port is zoned to two of node ports where each port comes from one node
canister. This gives four paths per host volume. More than four paths per volume are
supported but not recommended.
Improper zoning can lead to SAN congestion, which can inhibit remote link communication
intermittently. Checking the zero buffer credit timer from IBM Virtual Storage Center and
comparing against your sample interval reveals potential SAN congestion. If a zero buffer
credit timer is above 2% of the total time of the sample interval, it might cause problems.
Next, always ask your network provider to check the status of the link. If the link is acceptable,
watch for repeats of this error. It is possible in a normal and functional network setup to have
occasional 1720 errors, but multiple occurrences could indicate a larger problem.
If you receive multiple 1720 errors, recheck your network connection and then check the
system partnership information to verify its status and settings. Then, proceed to perform
diagnostics for every piece of equipment in the path between the two Storwize systems. It
often helps to have a diagram that shows the path of your replication from both logical and
physical configuration viewpoints.
If your investigations fail to resolve your remote copy problems, contact your IBM Support
representative for a more complete analysis.

10.12 HyperSwap

HyperSwap
The
power failure, connectivity failure, or disasters, such as fire or flooding. It is available on the
IBM Spectrum Virtualize, IBM Storwize V7000, IBM Storwize V7000 Unified, and IBM
Storwize V5000 products.
The HyperSwap function provides highly available volumes that are accessible through two
sites at up to 300 km (186.4 miles) apart. A fully independent copy of the data is maintained
at each site. When data is written by hosts at either site, both copies are synchronously
updated before the write operation is completed. The HyperSwap function automatically
optimizes itself to minimize data that is transmitted between sites and to minimize host read
and write latency.
If the nodes go offline or the storage at either site goes offline, leaving an online and
accessible up-to-date copy, the HyperSwap function can automatically fail over access to the
online copy. The HyperSwap function also automatically resynchronizes the two copies when
possible.
HyperSwap capability enables each volume to be presented by two I/O groups. The
configuration tolerates combinations of node and site failures, by using the same flexible
choices of host multipathing driver interoperability that are available for the IBM Storwize. The
use of FlashCopy helps maintain a golden image during automatic resynchronization.
Important: Because Remote Mirroring is used to support the HyperSwap capability,
Remote Mirroring licensing is a requirement for using HyperSwap.
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Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
high availability function allows business continuity in a hardware failure,