Are you in the band?
Where virtualisation is implemented in an appliance in the SAN, it may be categorised as inband (or symmetric) or out-of-band (or asymmetric). Inband means the I/O traffic travels though the appliance; out-of-band means it acts as a reference point controlling the flows without actually handling the data itself. IBM has initially chosen to implement virtualisation through an inband appliance as this allows for caching for improved performance and because it simplifies the task of making remote copies, says Barker. In future, the company may add virtualisation to switches and storage units.HP's CASA is an inband virtualisation device that controls and manages the data flows, so it can also handle replication, including replicating data from expensive disk arrays to lower cost devices, says Selway.
You need a combination of technologies to get the right price and the right level of redundancy, says Antal. "There are various pros and cons wherever the virtualisation engine sits." Palermo agrees: "Virtualisation can occur at any one of these levels, or all three," and each has a different value proposition.
File system challenge
Barker says the next issue to be addressed is the provision of a common, open standards-based file system. Due by the end of the year, IBM's SAN File System (previously known as StorageTank) provides a single file system with a single namespace. Every file is visible in a single directory tree regardless of the platform used to create it, which means all file administration can be done from a single console.
It also provides better file sharing between platforms, which may avoid the need to replicate files between different operating systems, decreasing the administration load and improving utilisation. Additionally, SAN File System supports policy-based file placement to locate data according to assigned characteristics, allowing organisations to get the most value out of different storage devices. According to Barker, it also integrates with management software (such as Tivoli Storage Resource Management) that can determine if the required performance level for particular data is being met. If not, Tivoli SRM can inform SAN File System that a change is needed, and the latter will instruct the virtualisation layer to move the data to a more appropriate device.
How to get there
Kieran believes storage developments will occur in three phases. Phase one is virtualisation, which is about allocation, monitoring, and metering. Phase two is automated provisioning, so if someone says "I'm putting on e-mail for 5000 users," the system will deliver the appropriate resources. Phase three is policy automation--in two or three years' storage systems will automatically maintain service levels.
By the end of this year, Selway expects to see devices from companies like Brocade handling virtualisation in the fabric. Data replication functions will move into the switches, so organisations won't need separate replication products for each vendor's arrays. However, these vendors will add their own management tools to control the switches.
These new switches will also provide the flexibility of on-the-fly selection of Fibre Channel or IP on a port-by-port basis, giving organisations the ability to adopt iSCSI on a non-disruptive basis when the time is right.
Like current storage solutions, the first products built on this platform "will not be conductive to random plugging and playing," warns Blandini. Applications in the switching fabric will initially have single functions that work with specific qualified products, but "as time progresses, OEMs will have time to qualify more solutions and we'll see more products working together" although any-to-any qualification is unlikely. Further ahead, various combinations of products will be qualified to work together. Customers will call for interoperability by late 2004, he suggests, and "we expect leading ISVs will play a leading role in this."
Putting storage virtualisation into switches removes the bottlenecks and limitations of PC hardware, provides seamless integration with network infrastructure, increases efficiency and decreases management costs, he says. "The industry at large agrees the technology is moving this way."
Are we there yet?
Some players caution against taking vendors' current claims at face value.
"I don't like the term 'virtualisation'," says Hitachi Data Systems' Vic Madarevic. He says what is being promised is far from what is achievable today, and multiple vendors need to provide their pieces of the puzzle so customers can reap the promised benefits.
| -The world's not going to stop if you don't go for virtualisation today." |
It is important to look for openness, freedom of choice and the ability to take advantage of whatever aspects of virtualisation are available, because there is a risk of vendor lock-in with early virtualisation products, he suggests. Madarevic looks forward to the emergence of a range of products including switches, host software, host bus adaptors, and management software all based on the same set of open standards.
A recent Forrester Research paper (The Problem With Storage Management) warns "Some users believe that new standards like CIM/Bluefin will solve all of their storage woes. But this optimistic outlook belies the hard truth--standards are required but not sufficient." [Their emphasis.]
The reasons include:
- CIM's current limitation to discovery and monitoring means it will be years before standards-based tools can manage high-end services such as replication services; and
- Major vendors have implemented their own message buses for communicating between software and hardware components, and organisations with heterogenous environments will be forced to run one of each until the industry settles on a standard bus.
Furthermore, that META Group report also warns organisations about "dreamware" in the storage market and suggests storage virtualisation will not reach maturity until 2006-07.
For those who want to be on the leading edge, META Group's Kevin McIsaac says "We believe that the technology will start to mature though 2005 to support this."
Additionally, the limitations of early standards mean the verification of interoperability is required.
"IT organisations can reduce the risk of purchasing products by challenging and verifying vendor claims, especially in the early stages of the technology adoption cycle," the META report concludes.
"Bringing all the pieces together is a challenge," says IBM's Garry Barker. But he warns that open standards are essential for the integration of multiple vendors' products. Penn agrees, saying that vendors that attempt to stay proprietary will lose market share, and that people will not buy virtualisation products ahead of standardisation.
Not just for the big end of town
Although much of the discussion around storage virtualisation revolves around the management of vast data stores, it is not the preserve of large organisations. Regardless of their size, "companies will get the benefits of virtualisation as they buy new and up-to-date products," says StorageTek's Joan Tunstall.
IBM's Grant Smith says that while these issues were previously of concern only to the top 10 percent of companies by side, they are now being faced by medium-sized organisations. "The amount of data and complexity is increasing everywhere," he says.
Veritas' Mark Bregman observes that storage consolidation is occurring even in the Windows market, bringing a demand for management through virtualisation. This is partly due to a tendency for departmental systems to be brought under central control. And he notes a previous wave of consolidation driven by CRM and similar implementations was cut short by the slowdown in IT spending and today's focus is on cost containment. Despite that slowdown, organisations are still spending on storage and especially on storage software. "Our customers don't stop creating data," he observes.
Brett Chase, product technical specialist at CommVault, points out that some of his company's customers, especially those served by resellers such as Commander, have as few as five servers with perhaps a NAS unit as secondary storage and a Quantum SDLT library as the third tier.
"The industry is moving from 'backup to tape' to 'backup to disk' with subsequent tape archiving in order to satisfy audit requirements," says Chase.
"We're trying to virtualise away the management of the data from the administrator," he explains; you don't need to know exactly where the data is stored because the software takes care of it.
| -Regardless of their size, companies will get the benefits of virtualisation as they buy new and up-to-date products." |
"Ninety-five percent of restores are because a user has deleted a document," not because a server has failed, says Chase.
CommVault's approach (like that of some other vendors mentioned here) means specific agents are required for the particular file systems, databases, and mail servers in use, but it does allow the use of existing storage investments such as tape drives. "What we endeavour to do is give you one investment in the hardware and then provide the management."
IDC's Graham Penn has a simple rule for determining whether an organisation is a candidate for storage virtualisation: "It generally becomes obvious when the IT manager and the staff are working 16 hours a day."
Executive summary
- Storage virtualisation provides a separation between the logical and physical location of files and data.
- Ever-growing demands for storage present cost and management headaches that can be reduced by virtualisation.
- A storage hierarchy allows data to be stored on devices with appropriate cost and performance characteristics, and virtualisation simplifies the management of these tiers.
- Virtualisation can improve storage utilisation and allow administrators to provide applications with additional space on demand and without disruption
- The non-disruptive nature of changes to virtualised storage assists with the introduction of new storage devices and technologies.
- Storage management costs can be significantly reduced by virtualisation, allowing administrators to handle much greater data volumes. Policy-based automation plays a key part in achieving this, along with a single management console covering the entire storage environment.
- Expert systems (or similar technology) may emerge to optimise the physical location of data within a virtualised environment.
- Virtualisation may be implemented in the host, through an appliance, in switches, or within storage devices. Most bets are on the switch.
- Standards are emerging that should help interoperation of products from different vendors.
- While steps can be made towards storage virtualisation, analysts--and even some vendors--warn that not all the pieces are yet available.
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