Welcome to part 2 of our series about the WORST things you can do with a VNX5300 storage system. If you missed part 1 about using thin provisioning when thick provisioning is a better solution, then read up here.

These top admin mistakes for the VNX5300 storage system come from one of Reliant’s EMC VNX engineering experts, and we want to ensure that you can understand why these mistakes may occur and how to avoid them. So, what is another thing our engineering expert thinks is one of the biggest mistakes you can make with a VNX5300?

VNX5300 Mistake #2:

Oversubscribing a storage pool.

What does it mean to “oversubscribe” a pool?

Oversubscribing is essentially where you provision a pool that exceeds this physical storage media at that time. Now, the process of oversubscribing a pool is actually relatively common, especially when thin provisioning, so you may be wondering why our engineer says this is one of the worst things you can do with a VNX5300. Well, what is technically the big mistake is OVER-oversubscribing a pool – thereby exceeding the amount of physical storage actually available to your users at any one time.

Let’s break it down…

Say, for example, that you have 1TB of physical storage available, but you provision 2TB for that storage pool. That would mean that you are 100% oversubscribed with that storage pool. Now, this isn’t really an issue if your users never exceed that 1TB of your actual, available storage on your VNX5300 array. The risk is that your users may USE the 2TB that they believe is provisioned for them, but doesn’t actually exist at that time.

Oversubscribing a storage pool is more or less a risk-reward balancing act. The more people that are promised storage, or are part of your oversubscribing of the pool, the more you can leverage that storage array, but the risk goes up that they will actually use the storage space that has been promised to them and you’ll reach that number of oversubscribing your storage pool, without actually having the physical storage to make it happen.

What happens when you reach that not-so-magic number?

Ok, so your users came in with a huge influx of data and you weren’t prepared. You had subscribed the pool for 2TB, but only actually had 1TB available. So, what happens when you’ve surpassed the 1TB you actually have? The short answer? Bad things happen. At the very least, your storage will turn into a “read only” environment since new writes are being denied. At the worst, that whole pool – and all that is in it – may go offline. Not good.

What should I do then?

In and of itself, oversubscribing a pool isn’t a bad thing. It just requires that you closely monitor the situation so you know when to order new storage. When to order this storage will vary based on how quickly your storage is growing, whether or not you’re implementing new projects, and how long it takes to get the new storage purchased and implemented. But make sure you stay within the best practice of keeping a 10% buffer before you fill all the storage that you have available. This will prevent decreased performance and will give you time to get the new storage you need.

Need more storage fast?

Reliant Technology offers capacity upgrades for the VNX5300 storage system – including disk array enclosures (DAEs) and disk drives – that can ship the same-day. Get what you need when you need it to avoid decreased performance or a capacity crisis. To get upgrades for your VNX5300, contact one of our storage specialists or call 1.877.227.0828.

Now you know… so what are the other mistakes you can make with a VNX5300?

Now you know two of the biggest mistakes you can make with a VNX5300 – oversubscribing a pool and using thin provisioning when thick provisioning would be a better solution – according to one of Reliant’s EMC storage engineering experts. Want to know the remaining 3 worst things you can do with a VNX5300? Check back later to find out!

Want to know more?

Reliant Technology provides the in-depth product knowledge and expertise around all things storage. If you are looking to upgrade your existing systems, want support for your storage, server, or networking hardware, or want to learn more – reach out to one of our storage specialists or call 1.877.227.0828. We’re here to help!