Nothing has been more exciting in storage than following the constant evolution of SATA disk drives, watching their capacity grow and prices per megabyte shrink, thus easing deployment of SATA drives in the once forbidden realm of enterprise SANs.
Although SATA drive performance and reliability are still no match for that of the more rugged SCSI and faster FC (Fibre Channel) siblings, SATA drives have improved over their parallel ATA ancestors. They are carving out a rather large deployment area that spans across transactional and reference data. Their recent adoption for entry-level solutions aimed at SMBs and remote offices from heavyweights such as EMC and Hewlett-Packard strengthens the case for SATA, especially against SCSI, at the low end of storage networking.
Western Digital has been adding diversity to the SATA landscape with product lines that significantly improve reliability and performance, such the WD Raptor and, more recently, the Caviar RAID Edition drives.
Despite advancements, the debate about whether SATA storage has sufficient reliability to support enterprise applications will probably last for a while because each side has strong arguments. Moderate cost and fast transfer rates make SATA drives an excellent candidate for deployments, such as disk-to-disk backups where the quantity of storage available is more important than its quality. Using SCSI or FC for backup scenarios is typically overkill. Although these technologies offer more reliability, they are also more expensive.
Not surprisingly, many products are emerging that enable connecting SATA storage devices to servers using FC, SCSI, or the emerging iSCSI (Internet SCSI). Among them are the Adaptec iSA1500 Storage Array and the nStor 4700F.
Despite some similarities, these solutions are indicative of how broad and diversified the SATA market is. Both offer great value, excellent management software, and superb features, but the iSA1500 shines for its contained form factor while the 4700F excels in performance.
Connectivity is another distinguishing factor between these solutions: With its two 2Gbps FC ports, the 4700F can find a home in any corporate fabric. By contrast, the iSA1500 deploys the friendlier and less expensive iSCSI connectivity protocol.
Adaptec iSA1500 Storage Array
Who says that large storage capacity goes hand-in-hand with bulky arrays? Thanks to four 250GB Maxtor drives, the Adaptec iSA1500 offers a roomy usable capacity close to 1TB in just a slim, 1U box.
The iSA1500 enclosure hosts 1GB of memory; a 1.6GHz Pentium processor; two GbE ports for data access; and KVM connectors, which ease local management via CLI. Overall, the unit is well put together; my only gripe is that its fans are a tad too noisy.
The same CLI is also available via serial port and Telnet. The array has a dedicated NIC for LAN-based remote management. In fact, by pointing a Windows machine at that LAN port, administrators can access Adaptec Storage Manager, a browser-based management GUI that overlaps most CLI features, leaving out only the most infrequent activities, such as the initial network configuration. Administrators can arrange the iSA1500's four SATA drives in various RAID levels, including 0, 1, 5, and 10, and they can easily set that configuration from any management interface. My unit came with all four volumes already configured with RAID 0 and I carved that space into several target volumes to feed to my servers.
Of course, I had to install Microsoft iSCSI initiator software on my Windows 2000 and Windows Server 2003 machines to access those servers. Usually, in order to manage an iSCSI SAN, you have to define new volumes on an array's management software, then move to the intended server to gain access to those volumes from the iSCSI initiator GUI.
It was a pleasant surprise to learn that Storage Manager includes a local agent that, installed on each server, made it possible to control my iSCSI SAN centrally and from a single GUI possible, eliminating annoying jumps between iSCSI targets and initiators.
In fact, after completing the installation, I simply gave Storage Manager the IP addresses of the iSA1500 and my servers before a diagram of my iSCSI SAN quickly appeared on my screen. From the same window, I created new logical volumes and, using the server agents as remote controls, I was able add those targets to the iSCSI configuration of each server.
Storage Manager and its agents offer the easiest approach to managing an iSCSI SAN that I have seen. The GUI is both simple to use and powerful. With the proper network settings, you can easily administer both local and remote iSA1500 arrays.
The standard Storage Manager license that ships with the array covers an extensive range of basic functionalities that should satisfy most requirements. The management software can be dynamically updated from its GUI to add features such as remote mirroring and more than 64 snapshots per volume, though I did not test this capability.
When I challenged the iSA1500 with heavy transactional load, the unit did not respond like a speed demon, so I would not recommend it for providing storage for busy transaction servers. However, the array can easily handle transfers of large volumes of data for operations, such as taking backup copies.
For example, using Iometer scripts to simulate backup operations, I measured a promising transfer rate of about 210MBps on its four drives. That transfer rate, which outperforms by several times even the fastest tape drives, suggests that the iSA1500 is a good choice as intermediate storage device for data protection. Adaptec recently completed the acquisition of Snap Appliance, which should help the company extend its offerings in networks storage.
Reasonably priced and with a compact form factor that can squeeze dozens of terabytes in a single cabinet, the Adaptec iSA1500 is a pleasure to manage and an easy entry point to start building an iSCSI SAN. Just don't seat anybody too close to it unless they have earplugs.
Similar to the Adaptec unit, the nStor 4700F makes a very good case for the affordability, capacity, and performance that SATA-based units can offer SMBs and remote offices, only on a larger scale.
The front of the 2U nStor 4700F can accommodate 12 SATA drives and is finished with a transparent bezel that provides protection while maintaining a free view on the control LEDs.
In the back of the unit are two 2Gbps FC ports, which make for easy connectivity between fabric or hosts and a built-in RAID controller. Interestingly, connectors and the RAID controller are mounted on an easily replaceable module that provides an alternative to FC, plain SCSI, and in the future, iSCSI host connectivity.
nStor offers similar flexibility on 4700's drives, offering a choice between maximizing capacity or performance. It's easy math: Mounting 250GB drives, the unit can reach an astonishing 3TB nominal capacity.
My test unit mounted 12 Western Digital WD740 Raptors, which amounts to a much smaller nominal capacity, less than 900GB. However, that configuration favors performance over capacity because those SATA drives are engineered to compete with SCSI units in speed and reliability. I was anticipating some exciting performance results from my tests with the 4700F.
I had only two servers connected to the unit, but running Iometer scripts to emulate a busy file-serving environment measured a consistent performance in excess of 1,800 I/O operations per second. Moreover, simulating backup operations with large buffer data transfers showed transfer rates as high as 290 MBps on the same machines.
After making the nStor unit consistent with my network from the CLI via serial port, I installed StorView, the nStor management application, on one of my servers. A few minutes were enough to learn how to use StorView and appreciate its comprehensive set of powerful features and friendly UI.
For instance, StorView automatically found my storage array and servers on the network, helped me avoid FC switch zoning, and connected servers to their LUNs from its GUI.
For SAN beginners, this is a blessing, because it removes the complexity of mastering the management software of FC switches. But it's always possible to take the more conventional switch-based route to administration.
I also monitored and configured the enclosure from StorView, which includes setting raid levels, defining hot spares, and creating new volumes.
Choosing a winner between Adaptec's and nStor's management apps is not easy. Both have great features but StorView wins in comprehensiveness and ease of use. For example, StorView sports a synthetic performance monitoring screen that displays data traffic in great detail and offers an intuitive, real-time view of the status of the 4700F and its components in a captivating animation showing the cooling fans spinning inside the browser.
Array-resident performance monitoring is one of my pet peeves but StorView goes beyond my expectations with detailed and interactive monitoring screens that group the load according to data block size, which helps relate the traffic to the originating application servers.
It's easy to predict that Adaptec will follow up on the iSA1500 with other SAN arrays; its excellent management software seems well-suited to managing arrays much larger than the current four drives. Nevertheless, if the current configuration satisfies your needs, piling up a number of iSA1500 arrays is an easy and affordable solution to protect data both locally and remotely. And don't overlook Adaptec's bundled snapshot capability and the optional mirroring app.
The nStor 4700F can satisfy most capacity and performance requirements with configurations that exploit its 12 bays with either large or fast SATA drives, such as the Raptor. In addition, the 4700F can easily connect to SCSI or FC hosts, with a promise to extend to iSCSI in the future. If you are looking for flexibility and robust management tools at a great price, the nStor 4700F is for you.