iSCSI for SBS – Part 1

Posted: May 28, 2011 in iSCSI, SBS 2011, Virtual Machines
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I have become a huge fan of iSCSI for use with SBS.  If you are not familiar with iSCSI, this first part of my posts will give you an overview of what it is and does and how it can be used.

iSCSI stands for Internet Small Computer System Interface.  SCSI has long been a favorite for high performance and reliable disk storage for servers.  There are several reasons for its popularity:

  • SCSI controllers almost always had RAID implemented to protect against single or even multiple drive failures.  Extra information was stored across the disk volumes to make certain that all the data could be recovered by replacing the errant disk.  Hot swap is also common, meaning that a drive could be replaced without stopping the system.
  • SCSI offloaded many of the processing tasks associated with reading and writing data to the controller rather than having the computer’s processor do all the work.
  • Data transfers from the device to memory were more efficient and often very much faster than for standard access drives.
  • SCSI disks themselves were often more rugged, faster and reliable than standard disk drives.

With high speed networks becoming not only the norm but very affordable, and with the need for shared storage among many servers, iSCSI came into vogue.  The controller and drives were now located in a separate box, and the commands to read and write and otherwise process the stored data were sent over the network instead of over a local bus.  Data to be read or written also travels over the network, and is done so with excellent efficiency.

Removing the disk drives from the server itself offers a great deal of flexibility.

  • It no longer matters where the server and controller/drives are located.  They can be next to each other, in different rooms, or across the country or world; response time and performance are still considerations, however.
  • Multiple servers can access the iSCSI device by using their network connections.
  • Servers “see” a disk on the iSCSI device as an allocated volume.  Volumes can be assigned from among a pool of drive space, and the remaining drive space can be used for other volumes on the same or different servers.
  • You can quickly create a new volume and hence drive for a special purpose on a server then as quickly delete it once you are done.  Think testing, making copies, and so much more.
  • iSCSI devices can be managed separately from the servers they provide storage for.

You might be tempted to ask, isn’t that just what a NAS device does?  The answer is no.  NAS devices provide file level access.  The server sees the files as a share, not a disk device.  While this may not strike you as being important, it certainly is critical for things like Exchange databases.  Exchange does not support storing data on NAS devices but does for iSCSI devices.  And for virtual machines, you are going to want to assign them drives, not folders.  More about virtual machines later.

While this is not an exhaustive list by any means, it will probably get you thinking about how cool it would be to have this flexibility for particular situations you have found yourself facing before.  So why don’t you have iSCSI already?

Historically, the answer was oh so simple: cost.  Storage area networks with iSCSI were outrageously expensive and could only be justified in some of the most business critical scenarios.  Think hundreds of thousands of dollars.  But after a while, the price came way down.  To tens of thousands of dollars.  Not exactly the budget range of most SBS installations.  If you are one of them who could afford it, please do call me, though, as I know we can work a deal.

Today, you can purchase a small iSCSI system for about the same price as a medium-sized NAS device.  As the size of an iSCSI system increases, you are going to pay about $800-$1500 more for the device over the cost of the individual disks.  Let me assure you that it is money very well spent.  I suspect you will save around half of it by more efficient use of your disk space.  I will have another post on selection and cost.

Well, cost aside, you might say, it is probably difficult and technically challenging to set up and use an iSCSI device.  Not at all.  Support for iSCSI is not only built into SBS, it is also built into Windows 7, and you may have occasion to use it with client computers in your environment.  I admit to having done so by needing a test or copy disk, which I allocated and attached in less than a minute.  It takes me longer to go grab a USB drive and plug it in.

While it may not be universally true of all iSCSI device manufacturers, many have provided great web based interfaces that are intuitive and easy to use.  When you first install the device, you have a few general tasks to do to get it ready to use.

  1. Set up the network connection.  Assign IP address(es) to the network adapter(s).
  2. Setup credentials.  Hopefully, your device will support the domain AD credentials, and it is a simple matter to provide the administrator credentials for the device to access AD.
  3. Initialize the storage for iSCSI if the device does not do it automatically.
  4. Create one or more iSCSI volumes.

To calibrate this effort, if you are not familiar with the interface, this might take 15 minutes.  If you are, maybe 3-4 minutes.

Once you have done this, turn your attention to the server.

  1. From the start menu, accessories, chose iSCSI Initiator.  You will see
  2. Enter the IP address you set up for the iSCSI device into the Target box and click Quick Connect.
  3. The targets will appear.
  4. Highlight the volume you want to use and click Connect.  The status should change to Connected.

That is how hard it is to get the iSCSI work done.  Let me repeat.  That is how hard it is to get the iSCSI work done.

But there is still the issue of making this volume a drive on the server.  To do that, you need to open Server Manager.  Once you have, click on Storage to expand, then click on Disk Management.  You should see something like this:

Note the unallocated disk at the bottom.  Right click on the Disk 7 (or whatever yours shows) area, then chose Initialze Disk.  Accept the defaults and click ok.

Now right click inside the disk space, create a new simple volume.  The wizard will let you assign a drive letter and to do a quick format. Once you are done, your disk is ready to use.

The next part of my iSCSI posts will discuss some practical situations on how to use it for a variety of applications and special circumstances.

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