5 – Best Practices
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13.After successfully logging in, you see the LUNs on the logged-in target as follows:
For Use Case 1, a new array object is formed. Issue the set array command to set the array
type and license the array if required.
For Use Case 2, the discovered iSCSI target paths appear on the previously existing array with
Fibre Channel paths. The Fibre Channel paths are offline, and the iSCSI paths are online. The local
router can now access the LUNs through the iSCSI paths.
4.3Discovering Remote Devices Through FCIP
The iSR6200 also provides an FCIP feature to discover remote devices. You can use one iSR6200 on
each site to create FCIP links and an additional router for migration. After Fibre Channel switches are
linked using FCIP, the remote Fibre Channel devices are available, just like any other Fibre Channel
device. The iSR6200 used for migration cannot differentiate between a remote or local Fibre Channel
device.
5Best Practices
For more information on general data migration best practices, see the Data Migration Service for
iSR6200 User’s Guide. The following guidelines describe the best practices:
Start online remote migration jobs during off-peak hours.
If the destination LUN is a thin-provisioned LUN, do the following:
Create new LUNs on the destination site.
In the GUI’s Data Migration Jobs Options dialog box, select the TP Setting option of “Yes without TP
Validation,” which does not copy zero blocks.
When using two iSR6200 routers (one at a local site and one at a remote site), set the migration I/O
size to 64kB. This setting accelerates writes by reducing the latencies involved with the write
command.
Use the bandwidth-limiting feature on the source array to throttle the migration, which in turn limits the
WAN link use.
When using two iSR6200 routers, issue the set iscsi command to manage the RTT and available
bandwidth. Tuning TCP window size based on the RTT is critical to enhanced migration performance.
You can calculate the typical window size in kB as follows:
WAN link bandwidth in MBps RTT in ms
Number of iSCSI connections between the iSR6200 and iSCSI target port of the storage array
For example, suppose the available WAN link bandwidth is 100MBps (1000Mbps), the RTT is 20ms,
and there are two iSCSI connections between the iSR6200 blade and the iSCSI target ports on the
storage array:
100 20 = 1000kB TCP window size
2
Configure a 1MB window size on the iSR6200 and iSCSI target port. The iSR6200 supports a
maximum TCP window size of 16MB. An iSCSI target array port may support larger TCP window sizes.