Dell Doubles Up NAS Clusters, But Can Push Higher

Network storage was invented decades ago because locally attached storage on systems was either too expensive or too difficult to share on those networks. NAS filers persist in datacenters today, and they are going to be around for the foreseeable future, because they are familiar, a lot easier to cope with, and usually less expensive than storage area networks. But to keep customers happy, NAS vendors have to keep moving up the capacity and performance curves.

This is precisely what Dell has done with its FluidFS file system, which is a NAS front-end for its EqualLogic and Compellent storage arrays and which has just been updated with a v4 release and plunked down on clustered appliances for scalability and resilience.

The FluidFS software was, according to the company, the fastest-growing storage product in the Dell line in 2014, and Dell got its hands on it five years ago when it bought the bankrupt remains of Exanet for $12 million. The Exanet deal gave Dell something to sell against clustered NAS suppliers like Isilon, which storage giant EMC acquired in November 2010 for a whopping $2.25 billion only months after Dell scooped up Exanet. Interestingly, the team behind Isilon has just uncloaked from stealth mode in a company called Qumulo to take on all scale-out NAS players with a shiny file system called QSFS that scales to more than 1,000 nodes and about two dozen petabytes of mixed flash and disk capacity. The Isilon OneFS 7.2 clustered NAS file system can scale even further, up to 50 PB, and delivers up to 2.6 million IOPS and 200 GB/sec of throughput in a NAS cluster.

Dell is not shooting that high, Mike Davis, director of file solutions, explains to The Next Platform. And the reason is that customers are just as concerned with cost and performance as they are with the scale of capacity in the clustered NAS arena these days.

The current FluidFS setup has been doubled up from 2 PB to 4 PB, and the redundant controllers running FluidFS and clustering the underlying Compellent or EqualLogic arrays have been beefed up with more memory as well. To be specific, the Compellent FS8600 appliances that implement the FluidFS file system, which supports both the NFS v4 or CIFS/SMB v2.1 file protocols, have the same pair of quad-core Intel Xeon E5620 processors as their main brains. Each node is mirrored in a controller pair for high availability, and has 48 GB of memory. This is double what the prior generation of FluidFS v3 appliances had, and Davis says Dell is just passing on the extra memory at no cost. That memory can help boost performance of the NAS, too. Depending on the performance level customers need, they can have from one to four FluidFS controllers (pairs of nodes), which are based on Dell’s own PowerEdge servers.

On a recent SPEC storage benchmark test, the SPECsfs2008 file serving benchmark to be specific, a four-node FS8600 clustered NAS head backed by the Compellent SC8000 arrays and SC220 storage enclosures. That loaded-up system was able to handle 494,000 SPECsfs file operations per second and deliver 11.9 GB/sec of throughput.


Dell can scale out the FluidFS software if customers need to push it. “With each release, we test a larger configuration, and there is no architectural limit in the file system,” says Davis. “So we are slowly and methodically extending the envelope of the product. In our next release, we may bump up the cluster size as well, but you have to impedance match both things. At some point it doesn’t make sense to increase the cluster size if you are performance limited by the number of spindles on the backend. We try to grow capacity and performance together.”

One popular option in the media industry, where Dell is selling a lot of FluidFS software and hardware these days, is to match up the FluidFS software with the Compellent SC8000 arrays and the SC280 disk enclosures, which cram 84 drives with 4 TB of capacity each into a 5U space. These nearline drives really drive down the cost, says Davis, and in the media industry in particular, customers are looking to get that cost down to around $500 per TB for a configured clustered NAS system. So a 4 PB system should therefore cost around $2 million. Most of that is for the disk capacity, since the FluidFS software running on a dual-node Compellent FS8600 controller costs only $25,000.

The other evolving use case for FluidFS is as the storage interface for server virtualization and desktop virtualization based on VMware’s ESXi hypervisor. VMware’s hypervisor could reside on an NFS file system, but with FluidFS v2, Dell has added in a plug-in for FluidFS for VMware’s vCenter Server management console and also has put in hooks for VMware’s storage array integration APIs, known as VAAI, so thin cloning and other functions of the disk array can interface with the hypervisor.

While Dell is selling VMware’s VSAN 6 hyperconverged storage, which we covered in detail back in February, for customers who want to stay completely in the VMware fold and run virtual SANs on the same nodes as their compute clusters, Davis says that Nutanix has a much more scalable hyperconverged platform and that Dell is aggressively reselling Nutanix on its XC hyperscale systems as a bundle.

“Hyperconverged tends to be disruptive,” Davis explains. “How do you migrate from a traditional environment to a hyperconverged environment? It is not straight-forward, they don’t mesh together all that nicely. So hyperconverged tends to be in greenfield, when customers are standing up a new datacenter with VM farms, or are standing up virtual desktop infrastructure for the first time, whether it is VSAN or EVO:Rail or XC running Nutanix.”

In those greenfield installations, particularly for VDI where the stack can be managed by a single administrator. With server virtualization backed by proper NAS or SAN hardware, there are storage, server, and network admins who have control over these aspects of the systems, and large enterprises have the skillsets and leverage with vendors to get their wares at a decent price to go with a best-of-breed setup. Large customers tend to stick with NAS or SAN, and in the mid-market, customers can go either way.

FluidFS v4 is not yet available to front-end Dell’s EqualLogic arrays, but will be later this year.

One last thing: The FluidFS is not to be confused with Dell’s Fluid Cache for SAN, which is a separate product based on another acquired clustering product, in this case from RNA Networks. Fluid Cache for SAN is used as a zippy cache front end for Compellent storage arrays serving up block-level workloads, such as relational databases. That Fluid Cache for SAN software was released last summer and has a similar architecture, hardware-wise, with a maximum of sixteen nodes acting as a cache on the front end of the Compellent arrays.

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