Application Note
Remote Data Migration for iSR6200
Products Affected
QLogic Storage Router
iSR6240
iSR6250
iSR6260
1
Introduction
This application note provides instructions for performing remote data migration using the QLogic
iSR6200 Series of intelligent Storage Routers listed in the Products Affected table. These routers are
collectively referred to as the iSR6200 throughout this application note. The iSR6200 command line
interface is referred to as the CLI, and the SANsurfer
throughout this document.
Remote data migration jobs are run as asynchronous mirror operations. During the initial copying
phase of remote online migration, the iSR6200 tracks I/Os occurring in the already copied blocks by
creating dirty region logs (DRLs). Remote online migration also keeps track of the I/Os after the initial
copying phase and creates DRLs. The DRLs are stored in the data management LUN (DML). After the
initial copying phase is complete, the DRLs are flushed continually.
®
Router Manager utility is referred to as the GUI
2
Prerequisites
Before configuring remote data online migration jobs, you must configure the DML on the iSR6200. If
you choose to migrate to a remote array in the offline mode, you need not create a DML. DMLs created on
one blade are available for remote migration jobs across both blades. You can configure up to eight LUNs
as DMLs. The maximum supported DML capacity is 2TB. For more information, see the Data Migration
Service for iSR6200 User’s Guide.
3
Remote Migration Use Cases
The iSR6200 supports the following use cases for remote migration. Section 4 Configuration provides
details on setting up the iSR6200 for these use cases:
Use Case 1: The source array is at the local site, and the destination array is at a remote site.
Use Case 1 typically applies to scenarios where the servers in a data center at Site A (the local site)
are moved to a data center at Site B (the remote site) and the data storage associated with the servers
are consolidated with existing or new storage arrays at Site B.
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4 – Configuration
Use Case 2: The source and destination arrays are at the local site initially.
For Use Case 2, after the initial copying operation, the remote migration is moved to the remote site.
The iSR6200 supports a maximum of eight paths per array. When using the topology described in
Section 6.1 to connect to the remote array, the array on the local site supports a maximum of four paths
if the destination array is a Fibre Channel array. The iSCSI presented targets are added as additional
paths to the existing array when the local Fibre Channel array is moved to the remote site.
Ta bl e 3 -1 summarizes the remote device connectivity topology for various combinations of supported
source and destination array types.
Table 3-1. Remote Device Connectivity Topology
Top olo gy Source Array
1 Fibre Channel or Fibre
Channel over Ethernet
(FCoE)
2 Fibre Channel or FCoE iSCSI Online or
3 iSCSI Fibre Channel
4 iSCSI iSCSI Offline Native iSCSI
Destination
Array
Fibre Channel
or FCoE
or FCoE
Remote
Migration
Method
Online or
offline
offline
Offline iSCSI presented targets or FCIP (see
Remote Device Connectivity
iSCSI presented targets (see Section
6.1) or Fibre Channel over IP (FCIP)
(see Section 6.2)
Native iSCSI (see Section 6.3)
Section 6.4)
4
Configuration
The following sections describe the configuration for remote data migration:
4.1 Performing Remote Migration
4.2 Configuring Local and Remote iSR6200 Routers for iSCSI Presentation
4.3 Discovering Remote Devices Through FCIP
4.1
Performing Remote Migration
Topology
To perform remote data migration, follow the steps in the Data Migration Service for iSR6200 User’s
Guide’s chapter on performing data migration, except for discovering the destination LUNs for migration.
This exception applies to the following topologies:
If you are using Topology 1 (see Section 6.1) or Topology 3 (see Section 6.3), follow the steps in
Section 4.2 for discovering your destination migration LUNs.
If you are using FCIP (see Section 6.2), establish the FCIP link, and then follow the steps in the Data
Migration Service for iSR6200 User’s Guide’s chapter on performing data migration.
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4 – Configuration
4.2
Configuring Local and Remote iSR6200 Routers for iSCSI Presentation
To configure local and remote iSR6200 routers for iSCSI presentation, follow these steps:
1. Identify the destination array ports to use for remote migration.
2. Zone the destination array controller ports with remote iSR6200 Fibre Channel ports.
3. Register the remote iSR6200 Fibre Channel ports and provide access to the LUNs on the destination
array.
4. Rescan the targets on the remote iSR6200 to discover the LUNs that were mapped to iSR6200 Fibre
Channel ports on the array.
NOTE:
Some arrays do not allow an iSR6200 Fibre Channel port to port log in (PLOGI) to its Fibre Channel
ports if there are no LUNs mapped to the Fibre Channel port that is logging in. You must generate a
registered state change notification (RSCN) to iSR6200 Fibre Channel ports by disabling and then
re-enabling all connected Fibre Channel ports on iSR6200 blades.
5. Ensure that the destination LUNs are mapped to the remote iSR6200 by issuing the show luns
command on the CLI, or by selecting the FC Discovered Targets or the iSCSI Discovered Targets node
in the GUI’s router tree to see the LUNs.
6. Configure the IP addresses, gateway, and subnet mask in the iSCSI interface(s) on the remote
iSR6200.
7. Configure the iSCSI interface(s) on the local iSR6200 as follows:
a. Configure the IP addresses, gateway, and subnet mask.
b. Set the iSCSI maximum first burst to 64K.
c. Configure the TCP window size for the round-trip time (RTT) and bandwidth to the remote iSR6200.
8. On the local iSR6200, issue the iscsi discover command in the CLI, or use the Discover iSCSI
Target Wizard in the GUI to discover the remote iSR6200 iSCSI port IP address.
9. Verify that the remote iSR6200 shows the local iSR6200 router’s iSCSI qualified name (IQN) by issuing
the show initiators iSCSI command in the CLI, or by viewing the Discovered iSCSI Initiator node
in the GUI.
10. Provide the destination LUN access to the local iSR6200 by following one of these options:
Disable LUN masking on the remote router using the set system command in the CLI (a reboot
of the remote iSR6200 blades is required).
Mask LUNs using the Target Presentation/LUN Mapping Wizard (on both blades) of the remote
iSR6200, presenting the destination LUNs to the local iSR6200 iSCSI initiator IQN.
11. On the local iSR6200, log in to the remote iSR6200 iSCSI targets by issuing the iscsi login
command in the CLI, or by selecting the targets in the iSCSI Discovered Targets node on the router tree
in the GUI.
12.Repeat the login using multiple local and remote iSR6200 iSCSI ports to enable multipathing between
the local and remote iSR6200s.
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5 – Best Practices
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.
4.3
Discovering 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.
5
Best 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
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
RTT in ms
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.
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