Best Practices for iSCSI High Availability
To allow mirroring over iSCSI, you must configure at least one active iSCSI initiator connection between the primary storage server and its partner. For multi-pathing over iSCSI, each storage server must have at least one active iSCSI initiator connection to its partner.
Here are some recommendations for using SANsymphony iSCSI High Availability:
-
If mirroring over iSCSI, storage servers will act both as initiator and target.
-
Set up a private LAN for iSCSI disk I/O for best possible performance; otherwise, your disk I/O will be subject to delays imposed by general traffic.
Multiple IP gateway addresses cause issues in Windows. When forcing iSCSI over the private network, a gateway address is not needed.
-
Set up a dedicated LAN connection for synchronous mirror traffic (direct connected or switch connected). Synchronous mirroring over a general traffic LAN is not recommended.
-
If you intend on setting up the Windows application server for HA using MPIO, then install MPIO before mapping third party AP volumes to the application server.
-
We recommend each storage server having three NICs and each application server having two NICs.
-
Use different static subnet addresses for each NIC used as a mirror path or iSCSI target.
-
If you are using multiple NICs for iSCSI storage on storage servers or application servers, we recommend that you set the following properties for these NICs:
CAUTION: Do not make these changes for NICs used for general traffic.
-
Use only Internet Protocol (TCP/IP). In Properties, select only Internet Protocol Version 4 (TCP/IPv4).
-
Do not register the NIC addresses with DNS. In the DNS tab in Advanced Properties, clear the Register checkbox.
-
Disable LMHOSTS lookup. In the WINS tab, clear the Enable LMHOSTS lookup checkbox.
-
Disable NetBIOS. Select the Disable NetBIOS over TCP/IP checkbox.
-
Set authentication Mode to CHAP (using the SANsymphony iSCSI Manager) for your general traffic NICs, so that application server iSCSI logons do not inadvertently occur over the general traffic LAN.
-
When using static TCP/IP addresses, log on to SANsymphony iSCSI targets using the TCP/IP address rather than the Hostname. This ensures that you will communicate over the correct network.