- Storage White Papers
This week, Microsoft released their iSCSI Target software for general availability. Previously this had only been available for installations with Windows Storage Server via OEMs. Now anyone with Windows 2008 R2 can install and use the software without restrictions. However, there are already a number of other iSCSI target software offerings already on the market, most notably from StarWind, iSCSI Cake and Kernsafe, so how does the Microsoft offering stack up? In this series I’ll look at each product and compare features and functionality, starting with Microsoft.
Installation of the Microsoft Target is pretty simple; it can be downloaded here: Microsoft iSCSI Target, then follow the instructions.
The Microsoft Target is configured through a MMC plugin that can be found under the Administrative Tools folder from the Start Menu (see screenshot 1). As the management tool uses a vanilla MMC window, it’s rather basic in appearance but follows standard conventions of right-click options to select properties or using the Action menu item. For instance, right-clicking on the Microsoft iSCSI Software Target displays a context menu and Properties option, leading to a two-tab dialog box. This allows the IP and iSNS details to be specified. In my example (screenshot 2) I’ve tied the Microsoft Target to a single IP address as all of the Target software products are deployed on the same server. There doesn’t appear to be an option to change the listening port, which defaults to 3260. iSNS server configuration is pretty simple, consisting of a list of either IP address or server names (screenshot 3).
Targets can be created by clicking on the iSCSI Targets tree item and selecting Action or right clicking. The configuration wizard asks for basic details such as the target name and default security details; specifying “*” for the IQN provides open access. In my test environment I created two targets, target0 and target1. These are shown in screenshot 4. The properties for a target allow configuration of security/authentication, performance parameters and virtual disks. Virtual disks use the VHD format and can be either fully provisioned or differencing. Unfortunately thin provisioned VHDs are not supported, which is disappointing (see screenshot 5). Once created, virtual disks are associated with a target and exported for use. One or more LUNs can be associated with a Target (as is standard with SCSI). These appear to the hosts as separate devices. The benefit of having multiple LUNs to the same target is that security is performed at the target rather than LUN level. Therefore access to one or more devices can be performed once on the Target. Screenshot 6 shows the two targets configured and idle (no connected hosts), with screenshot 7 showing a single target login. There doesn’t appear to be a way to find the logged in initator for a target although this may be available via WMI (still under investigation).
A point in time (PIT) copy of a LUN can be created using snapshots. Each snapshot represents a copy of the LUN at the time the snapshot was taken and can be used to return the LUN to a previous state. Alternatively the snapshot can be exported via another target or mounted to the iSCSI Target host itself. Either way, these LUNs are read-only copies and can’t be modified. Screenshots 8 and 9 show the snapshot list and a schedule to create a daily snapshot of Virtual Disk 0.
The Microsoft iSCSI Target offers basic functionality with the ability to add snapshots. Not being able to use thin provisioned VHDs is disappointing, however the underlying filesystem could be placed on thinly provisioned disks, but that may defeat the point of presenting storage using the iSCSI Target. Of course the iSCSI Target is free and free is (almost) always good.
Next post: StarWind iSCSI Target
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