Blade servers and virtualisation

By Todd Erickson
Wednesday, 10 June, 2009

The latest generation of blade storage products offer data management features such as thin provisioning and data deduplication that previously have only been available in external storage systems. Also, the introduction of virtualisation technologies to blade storage systems may increase its popularity among SMBs that seek easy installation, easy administration and advanced data services features. However, blade storage products come along with some inherent limitations.

Blade storage limitations

Blade storage solutions have historically faced market resistance because of connectivity limitations, capacity restrictions and the lack of advanced storage and data management features.

"The blade form factor constrains storage," said Jeff Boles, senior analyst and director of validation services at Taneja Group. "It constrains your ability to manipulate the storage. Your blade is only going to be so big; it's only going to have so much disk space on it. It's only going to be able to service so many clients; it's only going to be so connected to your infrastructure, and it's only going to have so much intelligence to manage it. It's a pretty limiting form factor."

Possibly the most imposing hurdle to widespread market acceptance is blade storage's inability to expand to meet a growing organisation's needs. "The inability to reach beyond the boundaries of a single blade has been a huge deterrent [to blade storage adoption]," said Boles. "Until we have more solutions in the market that can reach beyond the bounds of a single blade, we're not going to see blade storage solutions being applied very broadly."

Capacity restrictions are another reason blade storage has had limited success. "When we look at storage inside the enclosure, it's typically very purpose-driven because you have smaller capacities inside that enclosure," said Lenore Adam, senior product manager for Hewlett Packard's (HP's)StorageWorks. "Typically, if you are going to have a lot of capacity requirements, you are probably going to go with external storage."

According to Adam, typical blade deployments include:

  • Remote offices, such as retail outlets and enterprise branch offices
  • Departmental installations, where departments are responsible for their own computing and storage equipment
  • Short-term capacity expansion, where an IT department might need to get an application up and running quickly and can't wait to integrate the application into a full-blown storage area network (SAN) or network-attached storage (NAS) environment until later
  • An inexpensive tiered storage to house physical and virtual images

According to Boles, the most important criteria for comparing blade storage solutions is the amount of I/O operations per second (IOPS) the solution can deliver in the smallest form factor. Boles recommends that organisations look at the number of spindles each solution offers to service the storage blades I/O needs. That metric will undoubtedly change as solid-state drives (SSDs) are integrated into blade architectures, but the same principal will apply. Secondary buying considerations include connectivity to additional resources both inside and outside the enclosure, and the availability of advanced data management features, such as data deduplication and thin provisioning.

Next-generation blade storage

Today's blade storage products are nothing like their predecessors. Virtualisation and disk technology advances are allowing blade solutions to compete with mainstream enterprise storage systems while maintaining their smaller form-factors and efficiency advantages.

The main companies in the blade storage market are HP and IBM. HP recently introduced the StorageWorks X3800sb Network Storage Gateway Blade with the LeftHand Networks. P4000 Virtual SAN Appliance Software (VSA), bringing a virtualised infrastructure to blade storage. The X3800sb is a half-height blade system that uses 2.5-inch SAS or SATA drives. It supports 5,400 RPM SATA drives and up to 250 GB capacity (for a total capacity of 1.5 TB), 3 Gbps connectivity, and 10,000 RPM or 15,000 RPM dual-port SAS drives with up to 300 GB capacity (for a total capacity of 1.8 TB), and 6 Gbps connectivity.

According to HP's Adam, the P4000 VSA allows users to utilise the X38000sb as direct-attached storage (DAS). Also, users can build an iSCSI SAN within the blade architecture for greater shared-storage capabilities, allowing them to use advanced data services not typically offered in a blade system, including deduplication and thin provisioning. "These are all features that you typically get with external storage," said Adam, "so you should expect them with internal storage."

According to Adam, the P4000 VSA is installed on the computing blade and virtualises the physical storage blades just as server virtualisation virtualises physical servers. "The LeftHand Networks virtual SAN appliance turns storage blades into shared storage, basically into an iSCSI SAN, to be shared by any other physical or virtual server, either inside that enclosure or inside other enclosures over the network," said Adam.

According to Boles, the introduction of virtualisation to the blade architecture could generate a lot more interest in blade storage. "[Virtualisation] begins to make the solution much more compelling and much more like traditional storage," said Boles.

IBM's BladeCenter storage solution includes product lines for all organisation sizes. It features NAS and SAN products, and a tape library base. For SMBs, the IBM System Storage DS3000 product line includes systems with 12 drive bays in a 2U enclosure, and 3 Gbps SCSI, 1-Gbps iSCSI, and 4 Gbps Fibre Channel connectivity. It supports a 3.5-inch, dual-port, 15,000 RPM SAS or 7,200 RPM SATA disks, and can scale to 12 TB of total capacity with SATA disks and 5.4 TB with SAS drives.

The DS3000 can also expand using up to three System Storage EXP3000 expansion units for total capacity of 21.6 TB with 450 GB SAS drives, or 48 TB with 1 TB SATA drives. The EXP3000 is a 19-inch 2U enclosure that also supports 50 GB SATA SSDs. All of the units in the DS3000 product line also come with the DS3000 Storage Manager, which is designed for easy installation and administration, and start at $4,495.

Verari Systems'  SB165XL StorageServer appliance consists of a Verari SB1165XL server blade and up to four SB1058XL disk blades, which provides up to 48 TB of total capacity, and supports both NAS and iSCSI SAN functionality. It includes two 750 GB or 1 TB SATA II drives per disk blade with SAS connects, a web-based GUI, and 10 Gbps connectivity.

The SB1165XL also supports agents for third-party backup products including systems from CA and Symantec, and multiple advanced data services, including volume replication and snapshots, which sets it apart from most blade solutions.

Astute Networks Inc.'s approach to the blade storage market is rather different from making blade storage look like a typical SAN or NAS storage system. Astute focuses on the network edge and mobile data centers, and uses the advanced telecommunications (ATCA) industry-standard architecture for carrier-grade blade servers. "You're certainly not going to build a competing CPU blade with IBM," said Steve Knodl, Astute Networks' solutions architect. "That would be pretty foolish. We have a product that's unique and our technology is definitely different."

Astute Networks developed its own patented power reduction and cooling technology for remote installations and mobile data centers. The cooling apparatus moves the drive-tray heat onto a heat-spreader plate. Then active thermoelectric cooling elements move the heat from the drive's hot spots to areas with air flow.

Astute Networks uses an iSCSI TCP/IP offload storage processor, separate backplanes for power and data, and supports multiple backplane transport technologies, including Ethernet, Fibre Channel, InfiniBand, StarFabric, PCI Express, and RapidIO.

The Caspian R1110 is a 10 Gbps ATCA iSCSI storage blade that supports up to four drives per slot and uses standard 2.5-inch 146 GB SAS and 300 GB SATA drives from multiple manufacturers. Knodl said the company is evaluating SSDs, but has not settled on a specific model or manufacturer.

Are storage blades right for you?

While blade storage is a growing market with increasing visibility and reach, it remains a niche solution rather than a flexible storage strategy. According to Boles, prospective buyers should make sure that blade storage is right for their organisation before shopping.

"As a storage technology, is the fit right for you?" said Boles. "And by fit, I mean is the capacity and the I/O intensity the right fit for your needs?" Most blade solutions scalability are limited to what you get inside the enclosure, and adding more spindles to handle increasing I/O demands is not an option.

"If it is, then compare external storage and blade storage cabling, management complexity, power, and cooling costs," said Boles. "There's going to be some trade-offs when you go to blade storage, including some advanced storage management features like snapshots, thin provisioning, and deduplication -- some of the advanced capabilities you find in traditional SAN storage."

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