That guy or gal over there going on and on about spindles and IOPS – that’s your SAN admin. For the sake of your SQL Server environment, you two need to develop a solid relationship. Here’s some basic SAN lingo to get you started:
LUN is an acronym for Logical Unit Number. Each volume is assigned one of these when it is mapped from the SAN to your server or cluster. Think of this as the primary key for your volume.
If your storage is coming from a SAN, it is actually made up of multiple physical drives. The data is striped across this collection of drives to create a volume. LUN and volume are often used interchangeably among SAN admins.
How the data is striped depends upon the RAID configuration for the volume. There are a few standard RAID configurations, however many SAN vendors today have added their own secret sauce and created additional, non-standard RAID configurations. The important thing to remember is that the RAID configuration determines how redundant your data is, whether your volumes are geared more for read or write activity, and how fast that read/write activity occurs.
This is the acronym for I/O per second. The more you have, the happier your SAN admin is.
SAN technology today is pretty cool, and one of the coolest features out there is tiered storage. Newer SANs can be comprised of 7k, 10k, 15k and even solid state drives all in one unit. Not only that, but data can also move between these types of disks as demand for the data increases or decreases.
Not long ago, once a volume was created on a SAN, it immediately consumed that space from the available storage pool. Want to expand that same volume later on? Too bad – you have to create a new one and figure out how to transfer your data to the new volume. Thin provisioning solves this problem by allocating the storage blocks on the fly, as it’s needed. So even though Windows says that volume is 500GB, if your SAN is taking advantage of thin provisioning, only what is actually being used is consumed from the available storage pool. If you need to expand a volume, it can be done in a couple minutes.
When it comes to SANs, the controller is the brains of the operation. Controllers are typically servers that are loaded with SAN specific software and make sense of all the RAID configurations and determine what to do with incoming read/write activity.
Your SAN admin has a key hand in determining how fast the database environment you manage can be. You can tune queries and add indexes until your fingers bleed, but if you’re stuck on 7k disk with a 15k workload, you aren’t going to get very far. So tomorrow, when you pick up your morning coffee, pick up two and drop one off at your SAN admin’s cube.