When big conferences like Tech Ed come around, you never know what topics organizers find interesting. That's why really determined speakers submit a dozen or more every year, hoping one will make the A-list.
In submitting my dozen, the one selected was iSCSI and Windows Server: Getting Best Performance, High Availability, and Better Virtualization.
Configuring iSCSI for Windows Server, one can assume, is a topic many still find challenging. Or, at least, it's a topic whose configurations people have forgotten to remember. Remember these seven tips.
Tip You Forgot No. 1: Work from left to right. Working with the Windows' iSCSI Initiator control panel is more difficult than it needs to be. That said, it's the only control panel we've got. With six tabs confusingly-named Targets, Discovery, Favorite Targets, Volumes and Devices, RADIUS, and Configuration, inexperienced users may not know where to start. The expert knows the trick of working "from left to right," starting with discovering a target and eventually getting to volumes, RADIUS and that target's downstream configurations.
Tip You Forgot No. 2: iSCSI and Network Teaming don't mix, unless they do. iSCSI is most faithful when multiple connections are bonded together. That bonding protects storage access should a connection go down. Properly configured, it can also increase storage's maximum throughput.
Creating a bonded connection to most iSCSI SANs, however, shouldn't be done using traditional network teaming. Instead, use iSCSI's MPIO (Multipath Input/Output) or MCS (Multiple Connections per Session) protocols. MCS is automatically available, while MPIO requires its feature to be installed first, typically followed by a reboot.
One caveat exists: Rules are made for breaking and some iSCSI SANs actually suggest using traditional networking teaming. If that's the case, use it. Otherwise, don't.
Tip You Forgot No. 3: Connect and connect again. Creating multiple connections from a server's iSCSI initiator to the storage target is how MPIO and MCS add redundancy. However, the exact steps to add those connections to aren't always obvious inside Windows' iSCSI Initiator control panel.
That panel's Targets tab is the starting point for all iSCSI connections. It's this tab where one can identify the targets to connect to. After making a first connection, add more by highlighting that connection under Discovered targets and clicking Connect again. In the resulting screen, click the Advanced button and attach a second Local adapter and Initiator IP to a new Target portal IP.
In most configurations, although not all, create one-to-one mappings between Initiator IPs and Target portal IPs. Consult the storage manufacturer's documentation for what mapping of initiator IP to target IP their hardware requires.
Figure 1: Connect to Target's Advanced Settings
Tip You Forgot No. 4: Quick Connect isn't Good Connect. People must have complained about Windows Server 2008's iSCSI Initiator control panel, because that tool saw a minor facelift in R2. The facelift added a Quick Connect box to the Targets tab.
Entering in a target IP or DNS name and clicking Quick Connect attaches an iSCSI LUN to your server. The problem here is that the terms "quick" and "good" are mutually exclusive. Quick connection isn't likely to choose the most appropriate NIC for the job, nor will the connection be redundant. For connections intended to be permanent, use the Connect button. Make sure to correctly populate its three boxes with the appropriate IP settings (Figure 1).
Tip You Forgot No. 5: For NICs, IP then iSCSI. The iSCSI control panel doesn't care how you name the NICs. Whether their adapter settings call them "Storage NIC" or "VLAN 143," this information won't be found in the iSCSI control panel.
Take one more look at Figure 1. See how the Local adapter is set to Microsoft iSCSI Initiator and not an actual adapter name? This is usually the case unless a special iSCSI HBA is installed, which is a specialized NIC designed for storage networking.
Also in Figure 1, take note the Initiator IP displays only the NIC's IP address. This focus on addresses alone means one should always start any connection by first configuring each NIC's TCP/IP settings. Only after each NIC's TCP/IP is properly setup can one then continue with the iSCSI configuration.
Tip You Forgot No. 6: iSCSI and dynamic DNS don't mix. In every NIC's TCP/IP configuration is a checkbox titled, "Register this connection's address in DNS." Found under the NIC's DNS tab, this setting determines whether the DNS is dynamically updated with the NIC's IP. For iSCSI NICs, uncheck this box.
Once configured for iSCSI, a NIC is no longer in use for production networking. Checking this box means adding that NICs address to DNS. Doing so sets up a production networking round-robin among every IP address. Since the iSCSI NIC isn't listening for this kind of traffic, some clients won't properly connect to the server.
Tip You Forgot No. 7: If this advice conflicts with the manufacturers own advice, ignore these tips. Easily the most confusing part about iSCSI is the varying range of best practices found on the Internet. The advice exists in part because iSCSI's configuration depends heavily on the storage manufacturer's instructions. If any information there conflicts with what is found anywhere else, ignore everywhere else.
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ABOUT THE AUTHOR
Greg Shields is a Partner and Principal Technologist with Concentrated Technology, an IT analysis and strategic consulting firm. Contact him at http://www.ConcentratedTech.com.