Microsoft's Azure Blob Storage has overtaken Amazon's S3 as the top cloud storage provider, according to performance tests run by storage management vendor Nasuni.

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In 2011, Amazon was the clear leader. However in 2012, Microsoft edged ahead of its more well-established rival.

"Our tests revealed that Microsoft Azure Blob Storage has taken a significant step ahead of last year's leader, Amazon S3, to take the top spot," Nasuni notes in its 2012 annual report (PDF), which offers a set of benchmarks comparing the performance, scalability and stability but not price of five major cloud storage platforms.

Besides Microsoft's Azure Blob and Amazon's S3, the test included, by invitation, Google Cloud Storage, and two OpenStack offerings: HP Cloud Object Storage and Rackspace Cloud Files. The contenders had a chance to review the results, according to Nasuni.

Each vendor was benchmarked for write, read and delete performance under an evaluation that used a combination of file sizes from 1KB to 1GB and thread counts ranging from 1 to 50. The latter measurement was to factor in performance of file-server data which often has many small files.

Microsoft proved to have faster write and read speeds across file sizes up to 1MB, while Amazon topped the write speeds for files larger than 1MB. Interestingly, HP performed strongly across all three benchmarks, beating Amazon in the read benchmark for all file sizes, Nasuni said.

Amazon's write speeds on larger files may outperform rivals, but it lagged behind Microsoft, HP and Rackspace on read speads for files greater than 1MB.

To measure availability, Nasuni compared the response time to read, write, delete requests at 60 second intervals, factoring in retries and delays. Again, Microsoft performed the best, with an average response time of half a second over a one-month period, followed by Amazon's average of 0.65 seconds, while Rackspace came in at third with just under one second.

The one measure Google shone in was average uptime, sharing the top spot with Amazon's on-average 100-percent uptime. Microsoft was recorded at 99.996 percent, followed by Rackspace at 99.982, and HP at 99.977.

Stress test

The scalability tests compared how each platform performed write, read and delete while being loaded up "as quickly as possible" with new objects, maxing out at 100 million or 30 days, whichever came first.

"Microsoft was the only cloud storage platform to post zero errors during 100 million reads and writes" — Nasuni

Under this test, Amazon, Microsoft and Google did not show meaningful signs of stress, but it caused write speeds on HP and Rackspace — the two OpenStack platforms — to vary between 23.5 percent and 26.1 percent, respectively.

The OpenStack pair produced higher read error rates under this test, returning a small percentage where Amazon, Microsoft and Google produced none.

However, the clincher for Microsoft was that it was the only one that did not produce any read errors under the stress test.

"Not only did Microsoft outperform the competition significantly during the raw performance tests, it was the only cloud storage platform to post zero errors during 100 million reads and writes. In those categories where Microsoft was not the top performer (uptime and scalability variance), it was a close second," Nasuni notes.

Despite dethroning Amazon under the tests, Nasuni still considered Amazon a strong player and commended HP's performance as a newcomer.