Essential guide to hybrid flash arrays
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When the University of Colorado School of Dental Medicine (UC SDM) found the latency of its newly installed virtual application environment unacceptable, its IT team decided flash was called for and looked into whether it required an all-flash or hybrid array.
The school uses Axium accounting and project management software for most of its records. Jaymil Patel, UC SDM's director of IT, said he virtualizes Axium with Citrix System Inc.'s XenApp running on XenServer.
Patel said UC SDM typically has about 440 concurrent users logged in, and it can spike to 550 users. Students and faculty use the system to access patient records, images, appointments and billing records with Microsoft Windows 7 virtual desktops on Dell Corp.'s Wyse terminals.
After the school began using Citrix XenApp in early 2012, Patel noticed performance problems.
"It wasn't very long before they were hammering it," Patel said of his new virtual desktop setup.
Soon there were complaints about latency. After months of testing by the campus's central IT department and a visit from Citrix engineers, it was determined that UC SDM's legacy Dell EqualLogic iSCSI arrays caused the latency. Patel had 14 terabytes (TB) of usable capacity on the Dell arrays with 15,000 RPM SAS hard disk drives.
Using a low-end 10 IOPS-per-client baseline, Patel and his team calculated that they needed 6,000 to 8,000 IOPS from their storage system to effectively operate Axium on a daily basis, and the Dell arrays could not meet that need.
So Patel and Chris Ashburn, the school's senior business/IT professional, researched combination hard drive-solid state drive arrays along with all-SSD systems. Their finalists were hybrid arrays from Nimble Storage Inc. and Tegile Systems and an all-flash array from Whiptail Technologies.
UC SDM's requirements were enough IOPS to handle Axium, enough capacity to store regulated patient information and images, and the ability to handle multiple protocols -- all on an educational-institution budget.
When they compared the Tegile system with Nimble's, Patel and Ashburn liked Tegile's price and the fact that Tegile could work with multiple protocols.
"Tegile had a feature that we liked but that we haven't used yet," Ashburn said. "It can do NFS shares straight off the box. We won't have to buy hosts to attach to them."
The Tegile Zebi array can also handle iSCSI, Fibre Channel and 10 Gbps Ethernet. Nimble is iSCSI-only.
Patel and Ashburn also compared the Tegile system with the Whiptail all-flash array, but the all-flash system cost too much and had fewer features than Tegile.
UC SDM installed a Tegile Zebi HA2100EP array and J1100 expansion shelf in August 2012 and added a J2100 expansion shelf in January 2013. The array and expansion shelves all include flash, dynamic RAM and hard drives. Ashburn said UC SDM has a total of 26 TB of capacity, and most of that is not used. "We should be good for another five years with what we have."
Patel plans to add another Zebi system at the on-campus disaster recovery site he is working on. The DR site is under construction and scheduled to open by Aug. 2014. Patel said he would like to have the Tegile array in place and all the software loaded by the end of 2013.
That would give the dental school the option of setting up its own data protection and DR or use the university's central IT services.