There was a time when the iSCSI storage array was seen as purely an SMB product. This is no longer the case. With support from all the major storage vendors, as well as from a host of Tier 2 and Tier 3 storage players, iSCSI is now the most widely supported storage protocol available. And as more features and greater levels...
of functionality have been added to iSCSI SANs, their reach has stretched from the high-end enterprise to the small business and even the home user.
Beyond the platform support and the wider range of features than before, the iSCSI protocol has benefited from its ease of adoption. The protocol uses a standard Ethernet network, is transmitted using TCP/IP and is therefore simple to deploy across both the smallest and most complex network environments. At the host level iSCSI doesn’t need dedicated adapter cards. Microsoft has built an iSCSI initiator into the Windows platform, making configuration relatively simple. Almost all other major operating systems support iSCSI natively, too. Where performance is required, dedicated TOE (TCP/IP offload engine) cards can be used to reduce CPU load.
So what’s new in the iSCSI SAN market, and what trends will we see going forward?
10 GbE support
As a future trend, 10 Gigabit Ethernet (GbE) (and higher) will be the baseline in terms of network connectivity for iSCSI storage arrays. Today 1 GbE connections are already ubiquitous at the server layer with 10 GbE adoption in larger enterprises for managing workloads such as backup. Although most servers will not fully utilise their network capacity, 10 GbE interfaces at the storage layer will be essential to maintain performance and reduce congestion.
As a consequence, we see widespread support for 10 GbE from all the major iSCSI storage array manufacturers, including EMC (VNX, VNXe and VMAX), NetApp (FAS6200 and FAS3200 series), Dell (EqualLogic and Compellent) and HP (P4000 series). The two surprising omissions are IBM and HDS; the IBM Storwize V7000 series and XIV arrays currently only support 1 GbE connections; similarly, the AMS range also only supports 1 GbE interfaces.
One of the most obvious recent trends in the storage array market has been one of convergence. Previously, the market was split between those products offering purely iSCSI and those offering Fibre Channel. This boundary has become blurred to the point where most SAN arrays offer both Fibre Channel and IP-based (iSCSI and Fibre Channel over Ethernet, or FCoE) protocols. This has benefited the iSCSI SAN market by bringing high-end features to iSCSI storage arrays.
The most notable example of this is from EMC, with the recent launch of its VNX unified storage platform. VNXe products (VNXe3100 and VNXe3300) don’t support Fibre Channel, but they provide thin provisioning and data deduplication default with optional snapshots and replication.
As one of the leaders in iSCSI storage arrays, Dell has consolidated its position through the acquisition of Compellent. Compellent storage arrays (Series 30 and Series 40) support iSCSI with either Gigabit Ethernet or 10 GbE connectivity and provide advanced features including thin provisioning, snapshots and remote replication.
NetApp, which pioneered the use of iSCSI on storage arrays as one of the first vendors to offer iSCSI free of charge, is worthy of mention. Its FAS6200 and FAS3200 filers offer iSCSI with replication, snapshots, thin provisioning and data deduplication.
Another point of convergence is in products that offer iSCSI and NAS. The draw here is the ability to get block-level and file-level access in one device and using the existing LAN. Vendors offering this start at the low-end SMB-targeted sector of the market, such as Buffalo, Iomega and Netgear, but go up to midrange and enterprise products by traditionally NAS-focused vendors such as Isilon (now EMC-owned) and BlueArc, which now incorporates iSCSI into its NAS hardware.
The tendency toward convergence has raised the bar in terms of features for unified storage. It has also required the iSCSI-only players to raise their game and offer high-end features, too. Dell, through its EqualLogic brand, offers a range of products. For example, the PS6010XVS model provides 10 GbE support, 15,000 rpm SAS and solid-state drives (SSDs); the P6510X supports 10,000 rpm SAS drives; and the PS6500E supports large-capacity SATA drives. Features such as snapshots, thin provisioning, replication, volume cloning and multi-path I/O are common across the range.
HP acquired LeftHand in 2008 and rebranded the products as its P4000 series. The latest models all offer iSCSI 10 GbE support; standard and high-performance (15,000 rpm) SAS drives (although no SSD support); and a wide range of features, including thin provisioning, snapshots, clustering and “network RAID,” which joins multiple arrays together to perform a redundant storage infrastructure.
Where the Fibre Channel array market has moved to support virtual infrastructures, so the iSCSI market has followed. For VMware, VAAI (VMware API for Array Integration) is supported by EMC (Clariion), NetApp (FAS series), HP/3PAR, HDS (AMS series), Dell and HP (LeftHand). This is another example of convergence in array protocols bringing feature benefits for iSCSI.
As mentioned above, iSCSI is used across a range of markets. We have already discussed the EMC VNXe arrays, which specifically target the lower-end, sub-$10,000 market. This area is starting to see increased competition. Data Robotics recently released its business range of Drobo storage arrays; there are many other companies offering similar products, including Nexsan, Dot Hill (which also has an OEM relationship with HP) and Overland Storage.
The key to this part of the market is simplicity. Customers will typically not have dedicated storage staff and will rely on systems administrators to deploy and manage hardware. We have therefore seen a rise in simplified dashboard-based software management tools. Data Robotics arrays are managed through the Dashboard; EMC VNXe arrays are managed through Unisphere. These products use graphical interfaces rather than command lines to provide pictorial views of the hardware and to guide users through configuration and management using predefined wizards and other dialog screens.
iSCSI has come a long way since its introduction in 2000. Its ability to make use of existing networks has been a compelling proposition. We have seen iSCSI products mature to include enterprise features in products aimed at the midmarket, while the advent of SAS drives has brought performance that nudges at that of Fibre Channel but at an affordable price point. Key to future success will be the move to 10 GbE connectivity, which provides the bandwidth scalability required to match the increase in capacity iSCSI arrays now offer. In the future we can expect to see 10 GbE as the baseline standard for connectivity, followed by 40 GbE and 100 GbE support over time.
As vendors have moved to support multiple protocols within the same array, this convergence has made high-end features available to iSCSI, too. This in turn has forced the iSCSI-only vendors to introduce similar features to their products. Common features are thin provisioning, snapshots, replication and on some arrays, data deduplication.
iSCSI is starting to permeate further into the SOHO/SMB space with vendors introducing low-end iSCSI products to meet small-business needs.
Overall we should expect to see iSCSI used for some time to come. The next transition is likely to be the move to FCoE; however, as this protocol isn’t widely supported by network hardware, the change will be some time in coming, guaranteeing that iSCSI will continue to be the major IP-based block storage protocol in the data centre.