Options in small-business storage for server virtualisation

SMBs moving to virtualised servers need shared storage to support a new, dynamic environment. We survey the key file- and block-level options in small-business storage.

When a company's employee numbers grow into double figures, the need for multiple servers emerges. And the number of servers can quickly grow as the benefits of allocating one server per application becomes clear. Today, the most cost-effective way to do that is with server virtualisation, which provides the ability for one physical server to host multiple virtual machines (VMs), each of which can host an application server.  

When embarking on a virtual server project, small-business storage needs to be seriously considered. Reliability, availability and data protection are essential features, but cost effectiveness is a key criterion too. Instead of attaching storage directly to the server, which limits your expansion options, some form of shared storage will be required.

From a management perspective, with only a small number -- if any -- of IT staff, a single, shared small-business storage system reduces the overheads associated with multiple storage boxes attached to different servers. Each VM can then address storage in the same way, making it easy to add, copy and duplicate VMs as necessary. And it allows VMs to share storage if required and to move between hosts. A single storage device also simplifies backup and other administrative tasks.

File or block access storage?

A key decision when selecting small-business data storage is the method of accessing data, at either the file or block level. But, as we will see, it is quite common for vendors to include both forms of access in the same device.

Block-level access allows shared storage arrays to be viewed by the server hardware and software as if they were directly attached to the server. This approach is inherently more reliable and offers higher performance. It is well suited to the random I/O and high levels of throughput that VMs demand if they are not to appear sluggish and unresponsive to end users.

Block-level storage systems can be expensive, however, and can require a dedicated storage network and associated host bus adapters (HBAs) or iSCSI adapters. Block-level storage subsystems are sometimes called storage area networks, or SANs, for reasons that don’t necessarily apply any more but it’s a tag that’s stuck.

File-level access – aka network-attached storage (NAS) -- requires no dedicated network equipment, making it a more cost-effective approach more suited to small-business storage installations where performance considerations are secondary to cost or where only file sharing is required.

The traffic that busy virtual machines generate will adversely affect a production network, so to improve both performance and the security of the VM traffic, file-level storage will need a dedicated switch port to bypass production traffic.

Both file- and block-level access have pros and cons when it comes to supporting virtual server environments. After reviewing those advantages and disadvantages, you need to decide which one is best for your environment according to the likely workload, although many vendors (see survey below) sell small-business storage arrays with access via numerous block and file protocols in the same device. This are called a multiprotocol storage array, and although it incorporates both forms of access, you will need to decide whether they offer value for money according to the likely volume and nature of your storage workload.

Block protocol choice

If you opt for block storage, your choice of protocol will be determined by cost, performance requirements and your in-house skills.

Fibre Channel arrays offer the best available block-level performance. But, they’re costly and require dedicated networks (called fabrics), equipment such as HBAs and trained admins. For those reasons, Fibre Channel SANs are the preserve of larger enterprises.

The only real block access choice for smaller SMBs is iSCSI, which runs over Ethernet networks. It doesn’t necessarily need additional networking equipment -- though a separate physical network can be a sensible option -- and now can make use of the bandwidth of 10 Gigabit Ethernet. An iSCSI deployment needs to be well-thought-out in terms of networking and security, but the skills required are those that should be present in an organisation with existing Ethernet and TCP/IP-trained staff. iSCSI is well-supported with products for SMBs.

Some SMB storage products

Here we survey some small-business storage products. These products range from those aimed at very small businesses with so-called desktop NAS devices (although sometimes they include iSCSI access) through to SAN and multiprotocol devices aimed at the larger end of the SMB sector; these devices can include Fibre Channel block access, extra ports and capacity, plus greater processing power and enterprise-level features such as data deduplication, thin provisioning, snapshots and remote replication.

Buffalo Technology offers a range of NAS, iSCSI SAN and multiprotocol boxes under the TeraStation brand with disk arrays containing two to eight drives, plus two four-disk arrays, one in a minitower format the other rackmounted, both with iSCSI connectivity. They include backup; RAID levels 0, 1, 5 and 10; and UPS support. And all apart from the block-addressed iSCSI products provide support for file-sharing protocols CIFS, AFP, FTP, SFTP, HTTP, HTTPS and NFS.

Drobo's products are rare in offering the ability to add capacity using unequally sized drives to a RAID array, making them flexible to upgrade. The devices include data replication that can synchronise with another Drobo locally or remotely. Sized with either eight or 12 drives, two of the three-strong business range, the B800i and B1200i, are entry-level iSCSI SANs that offer thin provisioning, while the B800fs offers file access using CIFS and AFP protocols.

EMC's Iomega division produces devices with up to 12 drives under the StorCenter brand. The smallest, the px4-300d Server Class, has room for four drives and offers RAID levels 0, 1, 10, 5 and 5 + 1, as well as JBOD. At the top end, the iSCSI-capable, rackmounted px12-350r houses up to 12 drives; provides RAID levels 0, 1, 5 and 10 and JBOD; has four Gigabit Ethernet ports; and supports file-sharing protocols CIFS, NFS, AFP, FTP, TFTP, HTTP, HTTPS and WebDAV.

HP's multiprotocol storage systems for SMBs start with four-drive rackmounted systems and range up to the X1800 G2, which can house up to 16 2.5-inch SAS drives and has four 1 GbE ports. iSCSI is supported by HP's X34000 and X3800 products, which also offer a Fibre Channel option. All are based on Windows Storage Server and support data deduplication; indexing for Windows shares; replication; and file-sharing protocols SMB/CIFS, NFS, HTTP, FTP and WebDAV.

Infortrend's products include its ESVA series, consisting of a 16-bay Fibre Channel-connected SAN at the top end with eight Fibre Channel and four iSCSI ports. It also has enterprise-level features such as automated data tiering; and RAID levels 0, 1, 3, 5 and 6. At the low end is its EonNAS 3000 series. This offers multiprotocol support for CIFS, NFS, AFP, HTTP, HTTPS, FTP, iSCSI and Fibre Channel. Its features including thin provisioning; remote replication; and deduplication, a rare feature at this level.

NetApp aims its products at medium-size enterprises and above. The FS2200-series products support features such as data deduplication, thin provisioning and compression, along with many data protection features such as replication, snapshotting and data cloning (especially for VMs). The entry-level FS2220 houses 12 drives; has two controllers and eight 1 GbE ports; and supports iSCSI, NFS and CIFS. Its two larger siblings in the series, the FS2240-2 and FS2240-4, add Fibre Channel and twice as many drives.

Synology provides storage from two-bay enclosures with up to 24 hot-swappable drives. The product at the top end of its range supports iSCSI and features including servers for FTP, email, Web and print; an IP camera interface; and the ability to add unequally sized drives to RAID arrays. All products support iSCSI, a host of management features and VMware vSphere 4.x, while its top-performing DS3612xs supports all major hypervisors.

Manek Dubash is a business and technology journalist with more than 25 years of experience.

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