Practice with Xsan Admin

brandon's picture

Did you know you don't need access to a RAID to explore a fully functional Xsan Admin interface? It's really quite easy to walk through the various setup options without any significant hardware investment at all. All you need is a blank piece of storage media to label as an available LUN. A blank FireWire drive is ideal, though amazingly, an item as minimal as a USB key has narrowly sufficed. If you’re comfortable proceeding at your own peril, and if you don’t mind that your mileage may vary, here’s what to do:

First, install Xsan with Xsan Admin tools on the machine you’ll use. Next, choose a drive for the experiment, one that contains no data you need. Launch Disk Utility, select the drive, and click the Partition tab. From the Format pop-up menu, select Free Space and click the Partition button. This will make the drive’s capacity available for use as a LUN in your new minimal SAN.

Now, since the storage media you’ve just partitioned is no longer a disk format that OS X can mount, you may be prompted to Ignore, Initialize or Eject the media as you proceed. For now, simply choose Ignore.

Close Disk Utility and launch Xsan Admin. From there, you’ll be able to label your blank media as a new LUN, then add it to a new Storage Pool on a new volume to complete your minimal SAN. You can start and stop the Volume, mount & unmount it, dabble with affinities, the works.

While you won’t see anything impressive performance-wise moving data to and from your minimal SAN, you’ll have all the functionality you need for purposes like introducing a new tech to the interface, discussing setup options with a customer on the phone, or reminding yourself where a specific button resides. It’s surprisingly useful.

Down the line, when you’re ready to break down your minimal SAN and put your piece of storage media back into regular Extended Journaled use, you’ll need to launch Terminal and use the command line to ready that media for a reformat:

cd /Library/Filesystems/Xsan/bin/

sudo ./cvlabel –u "volumename"

Once you’ve done this to remove the volume label from the storage media you used for your minimal SAN, you may then erase that media normally in Disk Utility. The man page for cvlabel covers its functions in more detail for those interested.

Comments

7
aaron's picture

Can you stripe multiple disks together into a single storage pool?

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Aaron Freimark
Tekserve

Aaron Freimark
CEO, GroundControl

brandon's picture

Yes, you can stripe multiple disks together into a single storage pool with this
setup. As in the single-drive case above, each disk just has to be partitioned
as free space beforehand, and then unlabled afterward.

brandon's picture

Our colleague Joannou just brought up an important observation -- this
practice Xsan setup works as long as your IP address remains unchanged.
Xsan relies on static IP addresses for file system metadata communication. If
you are mobile or if you are practicing in a dynamic IP environment and your
IP
address changes, then your copy of Xsan Admin will not be able to find your
practice file system. You will then have to manually edit the following file with
your updated IP address to restore communication:

/Library/Filesystems/Xsan/config/fsnameservers

Nice catch, Joannou!

aaron's picture

Perhaps you can manually enter 127.0.0.1 into the fsnameservers file?

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Aaron Freimark
Tekserve

Aaron Freimark
CEO, GroundControl

ron's picture

Indeed you can Aaron.
Very handy for showing off the effect of using affinities.
Drives with flashing LED's help too.

The WWDC Xsan demostration did just that - using blinking lights on the RAIDs
to show that affinities were working :)

csoto's picture

Can't failover controllers if the new controller can't find the metadata! But
otherwise, it makes a good way to show affinities (user data only).