This is a good time to be buying a midrange storage-area network. Gigabytes per dollar is dropping, throughput per dollar is increasing and affordable systems are delivering sophisticated features that used to be reserved for the high end of the market.
Storage systems typically consist of three logical parts that may be in the same box or in different ones - a chassis that holds disks, a physical controller that interfaces the disks with the storage protocol, and a software management system. There are plenty of options: the chassis may support 12 to 48 SATA, SAS, Fibre Channel or SCSI disks, the controllers include hardware RAID at many levels, and vendors may support Fibre Channel, Ethernet or both.
We looked at four systems that represent a cross-section of the mid-range SAN market today:
- Compellent Storage Center 4.0, the highest-priced system of the group at just over $68,000. Compellent supports both Fibre Channel and Ethernet.
- Dell/EqualLogic PS4000, an iSCSI-only product at $17,000.
- HP StorageWorks 2000sa G2 Modular Smart Array, a Fibre Channel only product at $13,000.
- And a build-it-yourself combination of Promise Technology vTrak E610f with Datacore's SANMelody 3.0 storage software, a Fibre Channel and Ethernet system that runs less than $10,000.
You can expect some things from virtually any SAN system these days, including easy setup and quick integration into your existing data center. The high-end features that used to be the domain of expensive Fibre Channel systems are now available in the midrange systems we tested.
In fact, the Promise/Datacore system, the least-expensive product we tested, not only had all the features of higher-end products, it includes integration with VMware and some other features that the more expensive products have on their road maps, but not on shipping products.
So why buy the more expensive products? Peace of mind, primarily. For example, the Promise/DataCore system has no integrated support or warranty - you buy the system, some disks, a server to run the DataCore software on, and the assorted infrastructure parts (switch, cabling), and put it together yourself.
If you can't get it to work as expected, each of the six or more vendors involved is likely to point fingers at the others. If you're not sure what you're doing, it's easy to get SATA drives that really shouldn't be used in a RAID array, for instance. And optimising performance is not necessarily a simple thing - buying a complete system gives you components designed to work together.
The systems we tested are not direct competitors; they are all aimed at different parts of the storage market. In addition, each vendor offers a wide range of configurations that can produce systems from basic and inexpensive to very high performance and feature rich.
This test demonstrates the wide variety of functionality and performance available. For example, if you're looking for a very low cost iSCSI system, an EqualLogic system can be purchased with eight drives for around $10,000, while a high-end EqualLogic system can run $100,000 or more. The other vendors also offer a similarly wide array of options in the price/performance spectrum.
The rich feature sets are not simply about storage redundancy or high performance -- features such as automatic snapshots and synchronous or asynchronous replication can be used to replace add-on (and expensive) functions in other products, such as VMware or Microsoft's HyperV virtualisation software, for instance.
With these midrange SANs, you can easily replicate data from working VMs to a backup location and quickly get the backup site running if a disaster occurs, without a per-server license fee. Similarly, if you're using VMware for prototyping, testing or provisioning large numbers of servers for internal or external users, the ability to clone a VM volume and mount the clone as a new VM in a matter of seconds makes provisioning a snap.
Choosing a storage system is not a simple matter. Requirements have a way of evolving, not only in terms of the amount of storage required, but in terms of additional features for adding more performance, disaster recovery or high availability options to existing applications, or expanding from a test bed to an enterprise-wide system. Thus, it's important to look at not only the requirements you have now, but the ability of the system to grow with your needs.
Harbaugh is a freelance reviewer and IT consultant in Redding, Calif. He has been working in IT for almost 20 years, and has written two books on networking, as well as articles for most of the major computer publications.