Wednesday, February 13, 2013

Disk Shelves, RAID Groups, Aggregates and Volumes... Oh My!

Hi All,

Since NetApp does things a bit differently the concepts you might be familiar with traditional storage might be a little confusing when you begin to use your new NetApp controller.  So you've given everything an IP address it's available on the network, it's time to open up System Manager!

Aggr0 will have already been created and that's where ONTAP lives.  It's best practice to leave that guy alone, so the first thing you'll need to do is create your data aggregate.  So what's an aggregate?  It's just a bunch of disks chosen to go into a container.  When you create the aggregate you need to tell ONTAP what your RAID group size will be.  Now here's where it gets a little confusing.  When I first started working on this technology, I thought, "What is this number?", "How do I get it?", "Does my RAID group size and Aggregate have to be the same number?".  The best thing is to follow the recommendations of System Manager, which is usually 16.  The ONTAP engineers have done a lot of calculations on how to properly balance out load as capacity is added, but if you're unsure give your account manager a call, they'll help you set the best RAID group size for your environment.

Basically, RAID group size, is the number of data drives plus the number of parity drives, that's it.  So you can have more than 16 drives in an aggregate, it's a best practice to make that data aggregate as big as you can since you'll be using more drives to stripe your data to.  So what happens if you create an aggregate of 20 drives and have a RAID group size of 16?  16 drives will be data drives and 4 drives will be parity if you use RAID-DP, which is another best practice.  Still a little fuzzy?  Take a look at the drawing below.

Hopefully that helps clear up some of the confusion around RAID group size.  If not, let me know, I'll spend more time on it.  So you've created your aggregate, now what?  Next you'll create your Flex-Vol..  This is where all the magic happens and this is where you'll be spending most of your time.  Aggregates can grow and Flex-Vols can grow and shrink on the fly!  I won't talk much about LUNs and qtrees, but they fit inside Flex-Vols.

So there's a quick overview of some NetApp 101.  I hope it was helpful.

Until Next Time!

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