Monday, 02 July 2018

An Overview of Storage

An Overview of Storage

There are several different types of shared storage systems out there and they’re all good at different things. But what are they all and what storage should you go for?

Network Attached

The smallest and simplest option is Network Attached Storage (NAS). This is usually an all-in-one box - either on a desk or rack mounted - with 2-24 disks. Examples are the QNAP TVS series or the Synology Rackstation series. They’re simple to setup and manage - as well as low cost - but they tend to provide less performance and capacity compared to larger, more complicated systems.

Direct Attached

Direct Attached Storage (confusingly also sometimes called a NAS) is the next size up. This is a full-featured server with a larger number of disks (16-60). These are managed as any other server and don’t add a price premium over system and disks, and it’s usually possible to add expansion chassis to increase capacity. Performance will be good, but limited by the disk controller. The Supermicro Igloo is a popular mid-range storage server. 

Both of these systems are set up to deal with disk failures. However, because they’re a single appliance that makes them a single point of failure. Larger and more costly storage solutions all have some way to mitigate this risk.


A third option is the Storage Area Network (SAN). This involves connecting disk packs, servers, and clients to a low-level network (often fibre channel) that’s dedicated to storage. Quantum StorNext is a SAN system. This setup can allow very high performance as clients can access the disks directly over a dedicated link rather than go through another system. The downside is that this requires costly extra connectivity for all clients (i.e. another switch and network card) and there’s usually a software license fee as well.

There are two main types of clustered storage. These comprise several storage components connected together to form a larger, more reliable pool. The first option is a shared-storage cluster like Pixit Media’s PixStor. Two or more server nodes are attached to the same set of disk packs and linked together. Clients access the cluster as a whole and their requests are handled by any one of the nodes via load balancing. This allows consistent high performance for multiple clients as well as good redundancy. In the event of one of the nodes failing the slack is picked up by the others. However, this requires more expensive disk hardware with redundant controllers and a license fee.

The other type of clustered storage is a distributed storage cluster such as the Dell/EMC Isilon. Two or more storage nodes are connected over a high-speed network. Each node controls its own bit of storage. Clients connect to a node in the cluster and if it doesn’t have the data it will request it from another node. This setup is highly expandable as you can simply add more nodes for more capacity, and it scales well over high numbers of clients. It requires a separate data network between the nodes and there’s also a license fee.

The Cloud

Cloud storage is a different beast. Data is stored with a cloud provider like Amazon S3 or Google Cloud Storage. The provider handles redundancy and distribution and you just access files. Performance is limited only by the speed of your internet connection. You’re charged by capacity and time (i.e. 10Tb for 30 days) but this means you only pay for what you use instead of paying for empty disk space.

And it’s not just the style of storage you go for that has an impact on your infrastructure, but the type as well.

There are three types of storage drives.

Hard Disk Drives (HDDs) store data on rotating platters. A head moves over the platters to read and write data in circles or tracks. This means it can take a long time for the data you want to be ready to access (latency) and the performance is limited to around 150Mb/sec. However, a lot of data can be squeezed onto each platter so a single HDD can hold up to 12Tb and the cost per Tb is pretty low.

A Solid State Drive (SSD) stores data on flash memory chips. Data is written and read across multiple chips at the same time giving high performance and latency is low as there are no mechanical components. Capacity is, however, limited by the number of flash chips - usually up to 4Tb. Cost per Tb is much higher than for an HDD, but so is performance (around 550Mb/sec).

SSD performance is mostly limited by its connection to the rest of the system. The third type of storage is Non Volatile Memory express (NVMe). This allows flash storage to be connected directly to the PCIe bus, which enables much higher performance (around 3,000Mb/sec). NVMe drives are quarter of the size of an SSD so they can’t fit as many flash chips on resulting in a lower capacity slightly higher cost.

The style and type of storage you’ll opt for depends on a great many factors, not least of them being price, performance, and capacity. To learn more about the best storage for your workflow you can book a call with our storage specialists by completing the form below.

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