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Isilon adds snapshots, makes play for mainstream NAS

Users and analysts say Isilon's new snapshot features are a challenge to NetApp, but the NAS cluster specialist still has a way to go to compete in the enterprise.

Isilon Systems Inc. has released an update to its OneFS software for clustered network attached storage (NAS) that includes snapshots, bandwidth provisioning and improved failure tolerance. Users and analysts said the new features are a big step for Isilon toward giving Network Appliance Inc. (NetApp) a run for its money in the enterprise NAS space, but that certain features, especially backup using NDMP, still need improvement.

Taneja Group senior analyst Brad O'Neill said the addition of new software features, especially snapshots, are "critical" for Isilon to make inroads into the enterprise NAS space.

"Snapshots are a really big thing. No way can they sell into the enterprise NAS environment or the larger customer base they want to reach without snapshots," O'Neill said.

The new SnapshotIQ allows for up to 1,024 snapshots on the cluster, and the snapshots are performed in a way similar to NetApp's method, which stores only changes to files and uses very little CPU, as opposed to Hitachi Data Systems (HDS) and EMC Corp.'s snapshot option, the Business Continuance Volume (BCV).

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Meanwhile, Isilon is also differentiating its snapshots from NetApp's in terms of the number allowed -- 1,024 at the directory level and unlimited global snapshots; NetApp's limit is 255 per WAFL volume. Isilon also does not require the allocation or management of space for snapshots, since data is automatically distributed among cluster nodes. NetApp's FlexVol virtualization feature can perform a similar function, but its best practices generally call for the preallocation of reserve space for snapshots as well.

"It's great to have more granular backups than daily writes to tape," said David Kirchhoff, manager of information technology and senior geophysicist at Brigham Exploration Co. Previously, Kirchhoff said he had been doing host-based snapshots on a per server basis using Windows Volume Shadow Copy.

"That worked OK, but it was very cumbersome," Kirchhoff said. He added that the Isilon snapshots allowed him to set snapshot policies and schedules down to the file level, according him more flexibility than Shadow Copy in terms of which particular files he backs up and how often.

Moving toward a new customer base

Meanwhile, at least a few users not from Isilon's traditional high-performance computing playground have begun to pick up the system, including the county of San Bernardino, Calif., and broadcasting giant Clear Channel Communications.

According to Greg Robinson, solution architect for Clear Channel Communications, the company uses a 24-node, 35 terabyte (TB) Isilon cluster to store data from a farm of servers that host radio station Web sites. Robinson said the company also uses the cluster for files from EMC's EmailXtender email archiving software using SyncIQ, Isilon's replication software, and it is looking into adding a cluster in Denver for disaster recovery of corporate data.

Robinson said he had previously used EMC's Celerra NAS systems but had had difficulty upgrading capacity and experienced issues with file system scalability. He admits he's not the stereotypical Isilon user, but that the ability to add storage and throughput to the Isilon system won him over. Clear Channel is still using EMC for its primary storage area network (SAN) storage and plans to keep it that way.

"Even if Isilon added block-level access, in the form of iSCSI, I probably still wouldn't use it," Robinson said. "I don't think iSCSI is really an enterprise play, and we wouldn't have a use for it."

Robinson also said he missed one aspect of the Celerra clusters he had been using -- ease of use with NDMP. With the Celerra clusters, metadata could be transferred quickly to his Legato backup server over IP, while the backup data itself could be sent speedily through Fibre Channel (FC). Currently, Robinson said, the Isilon system has InfiniBand interconnects between nodes, but it still uses Gigabit Ethernet (GigE) out the back end, making NDMP for backups "not worth it" and not something he's using after trying it for a short time around a year ago.

"I would like to extend that InfiniBand performance to clients, namely my backup client," Robinson said. "I can still do my backups to tape from the cluster, but I could get better performance out of it."

Kirchhoff said he had been having problems getting NDMP to work at all with his Legato backup server.

"Legato supports NDMP but has not certified it with Isilon," Kirchhoff said. "They just need to get together and get the protocols and versions [right] so it will work better."

Currently, according to Kirchhoff, Brigham is backing up from a Network File System (NFS) mount on a separate Solaris 8 server. "It works fine, but NDMP would probably be faster," he said. "I'm not losing any functionality for backups, just some speed." That speed will become more important next year, when a new 3D land survey over 180 square miles of northern Texas and southern Oklahoma gets integrated into the San Antonio-based oil and gas exploration firm's storage system. The extremely dense data associated with that study, Kirchhoff said, will probably mean his Isilon cluster will have to at least double in size -- as will his backups.

Reached for comment with regard to the NDMP issue, Isilon spokesman Lucas Welch confirmed that Isilon does not yet have certification with Legato, but that it was in the process of qualification with both Legato and CommVault, and it already has been certified with Symantec Corp.'s NetBackup. "Isilon's customers have multiple ways of backing up and restoring their data," Welch added. "NDMP is just one option among several."

"Isilon's not quite ready yet for general purpose NAS," according to Tony Asaro, analyst for the Enterprise Strategy Group. "The core of the market is still not using them -- engineering development departments may have a home directory on Isilon, but the rest of corporate America isn't going to store their mission-critical data on their system."

Taneja Group's O'Neill added that if Isilon is casting an eye toward the enterprise NAS space, its technology should ideally also support block-level access as NetApp's NAS/SAN systems do. Archiving and compliance features would also be a plus, he said.

"Their scalability and performance story is awesome," O'Neill said. "They've already been able to make hay against NetApp in the high-performance computing market, and the work they've already done with NAS is not trivial."

Specifications on the new software

OneFS version 4.5 will now allow Isilon's IQ clusters to scale up to 96 nodes, with one petabyte possible under a single file system. According to Isilon founder and chief technology officer Sujal Patel, previously the biggest clusters in actual implementation belonged to, at 53 nodes. But, he said, many of Isilon's customers, who traditionally have been at the very bleeding edge of performance and capacity requirements, have surpassed cluster limits every time they've been raised.

With aggregate throughput, the new capacity ceiling for clusters means that the maximum performance for the IQ system has been raised to 10 gigabytes per second (GBps). Isilon has added greater failure tolerance to the system; now, up to three or four nodes (depending on a user's licensing of the software) can fail without downtime. Patel said the new failover design had been designed with the same storage overhead -- some 20% to 25 % of capacity -- as one- or two-node failover designs.

Lastly, the new SmartConnect feature allows users to zone bandwidth to portions of the cluster and to direct different traffic streams to different nodes of the cluster by virtualizing their IP addresses.

"This creates a DNS [domain name system] delegation zone and balances all the IPs by throughput," Kirchhoff said. "That's good, because it means that all the traffic isn't coming in on one specific IP address or node of the cluster."

The addition of the feature also quells some competitors' attempts to muddy the waters around Isilon. Clustered NAS newcomer Crosswalk Inc. came out swinging against Isilon this past April, calling its method of breaking up the file system through one node a bottleneck.

SmartConnect is available starting at $4,950 per node, and SnapshotIQ is available starting at $2,950 per node.

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