The US Army Medical Command (Medcom) has slashed user login times from five minutes to 30 seconds in an 11,000-user virtual desktop infrastructure (VDI) project with the help of Atlantis ILIO flash caching software from Atlantis Computing.
The Medcom VDI project spanned six hospitals in the US and Europe and its headquarters in Texas and has enabled it to serve virtual desktops and clinical applications to 11,000 users, including doctors on hospital rounds.
The key aim was to make access to virtual desktops and core applications more efficient for frontline providers on the move between and within hospitals, said Medcom virtualisation architect Lloyd Havekost.
“Login times used to take up three to five minutes of a 15-minute consultation, which was clearly a large chunk of a doctor’s time with a patient,” he said.
The VDI environment is built on VMware ESXi with virtual desktops provided by Citrix XenDesktop. Atlantis’s ILIO flash caching software sits in the hypervisor and directs Citrix virtual desktop images to cache memory in the server.
Each site comprises HP c7000 blade server chassis with BL460c G7 servers with hex-core Intel 5850 CPUs and 80 to 100 users per physical server. Bulk data storage is provided by a high-availability pair of NetApp 3270 filers at each site, with around 400TB of total capacity across all sites.
“When we create datastores and configure NFS on ESXi we point it towards Atlantis,” said Havekost. “This provides a cache – there’s 192GB of RAM on each server blade – that helps with reads and writes.”
Atlantis’s ILIO flash caching product addresses a key challenge with 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.
While Atlantis ILIO holds virtual desktop images and caches reads and writes, the bulk of user data is held on the NetApp filers that are in the same racking as the servers, with everything connected via a 20Gbps backplane.
Havekost said Medcom looked at just using the NetApp storage for the virtual desktops, but it was not quick enough for write operations. Atlantis was recommended by St Louis-based integrator World Wide Technology.
In any virtualisation project, determining the level of throughput to be supplied is a key metric. How did Havekost’s team decide what level of IOPS performance was required? Instead of averaging likely IOPS requirements Medcom decided it needed to provide for very high levels of throughput requirements, he said.
“Our doctors have throughput requirements between 10 and 200 IOPS, but we needed to find a way of getting 1,000 concurrent users logged in in a 30-minute window. Atlantis gave us the flexibility to do that with 200 IOPS each,” he said.
An additional benefit is that users can carry tablets and laptops between consulting sessions and stay logged into the same session without logging in again.