Council dodges £300,000 NetApp outlay with Atlantis flash caching

Bath and North East Somerset Council has avoided a £300,000 upgrade to its NetApp infrastructure by deploying Atlantis flash cache software on server RAM to power a virtual desktop infrastructure (VDI) roll-out.

The council – which has 2,500 across staff 75 sites – had NetApp storage in place for its VMware virtual server environment. But when a new 550-seat council building at Keynsham was planned, the authority’s IT department was forced to look at VDI to reduce energy consumption, said IT projects manager Leighton Ballard.

“The new building had to get desktop power consumption down to 30W per desktop. With our existing setup we were running at 200W per desktop,” he said. “So, we needed to look at thin client/VDI technology.”

When it came to storage to support virtual desktops, Ballard’s team ran into I/O limitations on the NetApp hardware. “We expected an average of 20 to 30 IOPS per desktop, which extrapolated out to requiring an extra 240 spindles on NetApp or 10 extra disk shelves at about £300,000, which was not feasible,” said Ballard.

The council’s IT team evaluated the options and eventually settled on Atlantis ILIO Persistent VDI flash caching software. This is deployed on 16 HP BL460 blades. The servers aren’t equipped with HDDs, having just 320GB of RAM with 90GB provisioned to Atlantis to act as a RAM disk for a VMware datastore for the VDI desktops.

The Atlantis flash caching product addresses a key challenge in virtual desktop environments, which is the massive and random I/O demands they place on storage.

With physical desktop devices there is unhindered access to direct-attached storage on boot-up and subsequently. But, with virtual desktops user configurations and data are served remotely, so I/O from users comes in randomly to the server and can be demanding in terms of volume of throughput, especially when many users log on at the start of shift, creating so-called boot storms.

The Atlantis flash caching product deals with this by directing virtual desktop images to reside in server cache, therefore ensuring rapid access.

Ballard said his team hadn’t been able to measure the benefits but he is convinced of an improvement in performance with the Atlantis software.

“We’ve no idea of the IOPS it’s able to handle, but in testing we ran IOmeter tests on Atlantis against an HP EVA that we were decommissioning with 56 Fibre Channel disks, and Atlantis beat it by an order of magnitude,” he said.

Ballard’s team considered other options before settling on Atlantis. These included adding flash and flash caching software to the NetApp arrays, but this failed to stack up in terms of cost or write performance.

“We also looked at HP blades with PCIe SSD, but this was costly and there was no inline dedupe so we would have needed a lot of capacity,” he said.

Overall, the benefits for the council have been that it saved money by not buying extra spindles for the NetApp arrays and the performance is better than it would be with traditional storage, cutting login times for users by about 10 times.

“We potentially took a risk with complex new software, but it’s been rock solid. We installed it, configured it and almost forgot about it,” said Ballard.