VDI issues: How to use SSD to improve performance
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After determining traditional storage arrays failed to keep up and all-flash is not yet worth the price, EU Services' IT team settled on a hybrid flash array to make its virtual desktop infrastructure (VDI) storage work.
EU Services, a direct mail marketing company based in Rockville, Md., installed 130 virtual desktops on a storage area network (SAN) for a pilot program three years ago to replace more than 100 PCs. But the company struggled with VDI's demanding storage requirements before swapping out its EMC Clariion AX-4 SAN for Nimble Storage's hybrid flash arrays in February.
After installing VDI, EU Services' storage choked at 50 virtual desktops. The company experienced boot storms in the morning and it took two or three minutes to boot a desktop, according to EU Services' Vice President of Information Systems Paul Nicholson.
"The SAN couldn't handle the [virtual desktops], which are very chatty," Nicholson said. "We went from RAID 5 to RAID 10 just to get the performance needed for workers to get their jobs done."
Nicholson said adding spindles to its VDI storage didn't help. Looking to flash for a boost, EU Services installed two Nimble CS220 storage arrays with 320 GB of solid-state drives (SSDs) for cache and 8 terabytes (TB) of hard disk drives. Nimble's Cache Accelerated Sequential Layout (CASL) architecture compresses primary data, increasing the effective capacity of solid-state and hard drives.
EU Services uses one CS220 system as its VMware server, running Microsoft SQL Server, Active Directory, Exchange, SharePoint and file servers, and supporting the VDI. The system replicates to a second CS220 for disaster recovery (DR). The second CS220 is backed up to tape.
EU Services now has 200 virtual desktops, but never has more than 130 running for locally connected and remote users. The virtual desktops access four servers running VMware View virtual machines. Since switching to Nimble, Nicholson said virtual desktops boot in less than a minute and boot storms have been eliminated. He said he can provision a virtual desktop in about five minutes.
"The cache stays healthy so there is not a lot of churning on the cache," he said of the Nimble hybrid flash system. "A reboot of the desktop takes 13 seconds. It can handle spikes up to 10,000 IOPS for 130 virtual desktops without the end user feeling any slowdown."
Nicholson claims EU Services saves $20,000 on backup infrastructure and software costs since shifting to VDI and Nimble. "The snapshots and replication are my first line of defense for my backup strategy," he said.
Before choosing Nimble for VDI storage, Nicholson said he had tested two all-flash arrays, but one system had reliability problems and the other had redundancy problems. "They were very fast," he said. "I could push one to 28,000 IOPS. Once the kinks are worked out, [all-flash arrays] are going to be unbelievable."
Dan Leary, Nimble's vice president of marketing, said 40% of the vendor's new customer wins during the first quarter of 2012 were for VDI deployments. He said last year customers were trying to save money on IT operations and it was difficult to justify the return on investment (ROI) for VDI.
"Now they have all these mobile workers that need to access applications from PCs, laptops," Leary said. "VDI is becoming an ideal way to leverage these devices. That is the big thing that is pushing VDI to the next level."