Briefing: Cloud storage performance metrics

by Jeremy

About 50% of business data is now stored in the cloud – and the volume stored using cloud technologies is higher when private and hybrid clouds are factored in.

Cloud storage is flexible and potentially cost-effective. Organizations can pick from the hyperscalers – Amazon Web Services, Google’s GCP, and Microsoft Azure – and local or more specialist cloud providers.Briefing

But how do we measure the performance of cloud storage services? When storage is on-prem, numerous well-established metrics allow us to keep track of storage performance. In the cloud, things can be less precise.

That is partly because choice brings complexity when it comes to cloud storage. Cloud storage comes in various formats, capacities, and performances, including file, block, and object storage, hard-drive-based systems, VM storage, NVMe, SSDs, and even tape, as well as technology that works on a “cloud-like” basis on-premise.

This can make comparing and monitoring cloud storage instances harder than on-premise and conventional storage performance metrics, such as IOPS and throughput. IT professionals specifying cloud systems must account for cost, service availability, and even security criteria.

Conventional storage metrics

Conventional storage metrics also apply in the cloud. But they can be somewhat harder to unpick.

Enterprise storage systems have two main “speed” measurements: throughput and IOPS. Throughput is the data transfer rate to and from storage media, measured in bytes per second; IOPS measures the number of reads and writes – input/output (I/O) operations – per second.

In these measurements, hardware manufacturers distinguish between reading and writing speeds, with reading speeds usually faster.

Hard disk, SSD, and array manufacturers distinguish between sequential and random reads or writes.

These metrics are affected by the movement of reading/write heads over disk platters and the need to erase existing data on flash storage. Random read-and-write performance is usually the best guide to real-world performance.

Hard-drive manufacturers quote revolutions per minute (rpm) figures for spinning disks, typically 7,200rpm for mainstream storage, sometimes 12,000rpm for higher-grade enterprise systems, and 5,400rpm for lower-performance hardware. These measures do not apply to solid-state storage, however.

So, the higher the IOPS, the better performing the system. Spinning disk drives usually reach the 50 IOPS to 200 IOPS range.

Solid-state systems are significantly faster. On paper, a high-performance flash drive can reach 25,000 IOPS or even higher. However, real-world performance differences will be minor once storage controller, network, and other overheads such as RAID and cache memory are factored in.

Latency is the third key performance measure to factor in. Latency is how quickly each I/O request is carried out. For an HDD-based system, this will be 10ms to 20ms. For SSDs, it is a few milliseconds. Latency is often the most crucial metric to determine whether storage can support an application.

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