Our Platform. Part 4: Storage

Wed 23 Oct 2013 | View all blogs

Storage plays a key part in any cloud platform. Often the bottleneck, a poor choice here can lead to a platform that won’t scale or deliver the performance that customers expect from an enterprise cloud host. This is the last in a four part series discussing our technology choices; in this part we’ll look at the storage components behind our platform.

We offer three tiers of storage, each designed to cater for specific requirements. Our “capacity” tier offers the lowest cost per GB, being designed for applications which don’t need high I/O but a lot of storage space. We use NL-SAS drives in a RAID-6 layout to drive down the cost per GB.

Our “performance” tier is what the majority of customer workloads run on. SSDs are used to accelerate I/O from an already fast SAS/RAID-10 storage pool. Benchmarking shows that our performance tier outperforms other cloud providers by a very comfortable margin without costing a premium.

The “extreme performance” tier is designed for the most demanding customer workloads; typically high transaction database servers. This tier is provisioned from all-SSD storage arrays and offers blistering performance.

EMC Storage

Whilst SSD/flash array vendors would have you believe that they can offer a cost per GB equivalent to that of a traditional disk based array, this has not been the case in our experience. No-one is doubting the performance and benefits of flash, however the reality is that general purpose workloads do not require the performance levels of all-flash storage and customers require more cost effective tiers of storage.

Traditional disk-based arrays aren’t quite dead, not yet. The use of a small amount of SSD to accelerate I/O has given them an extended lease of life whilst remaining affordable.

We had extensive discussions with EMC and Netapp and decided to go with EMC as we felt they had a stronger product when using block-based storage. We make use of features such as Fully Automated Storage Tiering and SSD cache/acceleration in order to offer our customers far greater levels of performance than is possible with mechanical disk based arrays.

As would be expected from EMC, their storage arrays are near bombproof, making use of multiple controllers, SAS loops, fabric interconnects and using only the highest grade SSD and hard drives.

Our “performance” and “capacity” tiers are provisioned from EMC SANs.

Pure Storage

We looked at Pure back in June 2012 but they just weren’t viable for us then. With no real UK presence we felt they were only suitable for US customers, but we loved their product and concepts so we kept in touch. In December 2012 Pure had expanded out of the US into many countries and had a dedicated sales and support office in the UK.

We trialled an all-flash array under their “Love your Storage Guarantee” and gave it an extreme workout, pushing its performance to the limits to see if we could break it. We could not. We love the fact that it’s built from Dell servers, very similar to our own. We love the fact they use Samsung and ZeusIOPs SSDs, our favourite choices. The results speak for themselves, something we’ll do a detailed blog article on in the near future, suffice to say I/O performance is stellar whilst maintaining consistent low latency.

Our “Extreme Performance” storage tier is provisioned from Pure Storage flash arrays.

>> Part 1: Servers
>> Part 2: Network
>> Part 3: Software
>> Part 4: Storage

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