How to turn one JBOD into two JBOD’s

When putting together a storage lab for study, one of the important components is the disk arrays.  For the purpose of CCIE Storage Study, the arrays may seem to be rather generic, and from the MDS perspective they pretty much are.  You don’t need anything fancy.  You can use public or private loop for example.  I prefer public loop simply because its fabric aware, and TL ports are not supported on Gen 2 modules, so I want to future proof my investment, especially since public loop JBOD’s can be had for so little.

There are reasons however for getting a better JBOD, it may in fact save you money, even though it may seem to cost more.  For example, it’s no secret that one of my favorite JBOD’s is the Xyratex RS-1600-FC2.  These are basically what NetApp uses as their DS14mk2 disk shelves.  These are public loop and seemingly basic, however they have some nice options for lab study, particularly the ability to be paritioned. There are many other JBOD’s that support this type of partitioning functionality.  For example the Sun StorEdge A5200 (and most later models) support this functionality.  I prefer the Xyratex unit over the Sun however, since its more readily available, less heavy, less noisy, uses less power, and produces less heat.  This concept of splitting a JBOD can be applied to many different disk arrays however.

Xyratex RS-1600-FC2

The RS-1600-FC2 has the ability to hold 16 drives.  These can be configured as a single 16 drive loop, or as two 8 drive loops.  When your using two loops, they are really completely separate from the MDS’s perspective.  It effectively views these two separate loops as two JBOD’s each with 8 drives.  Because the RS-1600-FC2 has two LRC modules, you end up with two ports for each loop to plug into your MDS’s, just as you would if you had two physically separate JBOD’s.  There is much advantage to this.  When your building a SAN lab, power, space, cooling and noise can really become an issue.  It’s not the type of thing you easily build in your house.  The biggest culprits of these environmentals are in fact the disk shelves, followed by the MDS’s, and lastly the servers and other support equipment.  Being able to reduce the number of power circuits to half, and not introduce any additional power supplies and fans is a big plus.  Also you don’t have to use the redundant power on the JBOD’s, they will work just fine with single power supplies plugged in, you can silence any alarms using the configuration screen or jumpers.  The net result, is that instead of purchasing say four separate JBOD’s for study, you can get away with 2 and have pretty much the same result.
Here is a look at the way this particular JBOD is laid out:

Xyratex RS-1600-FC2 Layout

You can see that the JBOD has redundant LRC’s, redundant power supplies, and redundant fans.  Notice how the drives are laid out left to right.  The drives can be partitioned so that drives 0 through 7 can bee on one loop and drives 8 through 15 can be on a second loop.

Xyratex RS-1600-FC2 Loop Configurations

To the left are the two different loop configurations supported on this particular JBOD.  Configuring these is very simple, via the use of a thumbwheel and set of jumpers on the back of the unit.  Xyratex refers to the 1×16 drive setup as Mode 1, and the 2×8 drive setup as Mode 2.  A decent setup would be to populate the array with at least 12 drives, 6 in each loop.  I find 6 to be a very useful number of drives for a JBOD and studying storage.  You could populate all the drives, but each drive does use more power and generate more heat, so something to take into consideration.  With our setup of 12 drives, we would populate drive slots 0-5 and drive slots 8-13.  Each loop would be setup in the same way.  I prefer to use small drives and typically finding drives that are 7200 or 10000 RPM would be preferable to 15000 RPM, since usually the faster the drives the more heat and power that is used.  There is not much benefit in using larger drives if its just for lab.  You can get small good drives for probably less than $10 each on ebay.  An actual RS-1600-FC2 based shelf unit can sometimes be had for as little as $100-$150.

Xyratex RS-1600-FC2 Switch Settings

You can see that the switch settings clearly show its a breeze to partition the JBOD.  Simply set switch 1 to “Off” and the JBOD will use a split 2×8 configuration the next time it is powered on.  Don’t worry that this is not the factory recommended setting, after all why would Xyratex want you to get two for the price of one :).  There are other settings you may want to configure such as the speed or the drive addressing.   Realize that on most JBOD’s like the RS-1600-FC2, there is no auto-detection between 1Gb/s and 2Gb/s, you have to set this manually.  You have to make sure your GBIC’s at both end support the speed as well, which with 1-2GB this usually is not a problem.

So this is one step toward making your study lab more affordable and more easier to manage.  It is also possible to virtualize the servers.  I am not talking about using NPIV however, as that would not be as appropriate in a SAN lab, but rather multiple physical adapters in a beefy server running ESX for example.  You could say run 3-4 hosts on a box like this, and put 3 dual port HBA’s in it, and have literally 1 server and 2 JBOD’s doing the work of 4 servers and 4 JBOD’s.  Unfortunately there is no way to virtualize the MDS’s or third party switches such as the McData and Brocades you will need.

If you are using a JBOD that supports this type of partitioning please comment.  I can tell you that the JMR Fortra arrays I use do not.  But I have the Sun A5200 and Xyratex arrays which do.  Also to note is there is a difference between the Xyratex RS-1600-FC and Xyratex RS-1600-FC2.  You want the FC2.  There are also some other models which may be RAID, and what you want in a CCIE Storage Lab is JBOD mode, not RAID.  So do careful shopping, ask questions and make some smart purchases.  Good luck in building your lab!

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