REVIEW: The Dot Hill 2722 is a 2U RAID storage array that can house as many as 24 2.5-inch drives accessible via dual 4Gb Fibre Channel controllers. eWEEK Labs' tests show that the system is a solid step into the smaller 2.5-inch form factor, with an easy-to-use GUI, good performance and a high-availability architecture.It is very hard to find fault with the Dot Hill R/Evo 2722. Its a
solid step into the smaller 2.5-inch form factor, with an easy-to-use GUI,
extremely strong performance and a high-availability architecture.
The Dot Hill 2722 is a 2U RAID storage array that can house as many as 24
2.5-inch drives accessible via dual 4Gb Fibre Channel controllers. By using
2.5-inch drives (which are 70 percent smaller than 3.5-inch drives), data
centers can pack more high-performance storage into a smaller space, use less
electricity, and generate less heat and vibration.
According to Seagate, a 2.5-inch drive can consume up to 50 percent less
power than an equivalent 3.5-inch drive. As the price of high-performance
2.5-inch drives decreases, expect to see more enterprise storage products shift
to this form factor.
Built on the same core architecture as the Dot Hill 2000 series product
family, the 2722 can support additional drive enclosures connected via SAS
to scale up to 96 drives. The unit I tested had dual RAID controllers, each
with Fibre Channel, RS-232, Ethernet and external SAS connections.
For performance and redundancy, each drive has dual SAS ports, with one
connected to each controller, and cache is simultaneously mirrored between
controllers. In addition, each controller cleverly avoids the use of
battery-based cache backup with four super capacitors and integrated Compact
Flash storage. The system also includes dual hot-swappable power supplies.
Pricing for the Dot Hill R/Evo 2722 starts at less than $15,000 for a
unit with 24 drives and a single controller. As configured for the review (dual
controllers, fully populated with 24 36GB 15K SAS drives), the system would
have a street price of about $19,000.
Smooth Installation
During tests, installation went smoothly. I installed a Qlogic QLE2562 PCI
Express dual-port 8Gb FC Host Bus Adapter in my Lenovo RD120 test server. (One
of the advantages of using a Qlogic HBA is the included SANsurfer management
and diagnostics software.)
I then rack-mounted the 2722 and made Fibre Channel and Ethernet
connections to both controllers. I was running Windows Server 2003, so I had to
install the Dot Hill DSM (device-specific module) to enable Microsoft Multipath
I/O; this is not necessary with Windows Server 2008, as support for MPIO is
built-in.
From my server, I launched a Web browser and connected to the 2722s
default IP address. I logged in using the default management user name and
password.
The Web GUI, or RAIDar Storage Management Utility, is well-organized and
easy to use; there is also a command-line interface.
Upon logging into the server, the first thing I saw was the System Overview,
which provides information on the health and utilization of the system,
enclosures, disks, vdisks, volumes, snap pools and snapshots.
Across the top of the frame are menus for View, Provisioning, Configuration,
Tools and Wizard; this meant that any task I needed to accomplish was never
more than two clicks away.
By clicking on Physical, Enclosure 0 in the Configuration View frame on the
left side of the browser, I was able to see a graphical representation of the
unit itself, with drive, controller, power supply and interface status
indicated in the proper place. Clicking on a specific drive makes its light
flash, which made it very easy to find my way around both the GUI and physical
unit itself.
I ran the Provisioning Wizard, which walked me through creating a RAID set
(or virtual disk) by selecting RAID type (the 2722 supports 0, 1, 3, 5, 6, 10
and 50), providing a name, associating with a controller and selecting which
physical drives should be in the RAID set.
Next, I initialized the vdisk, a task that can be performed online (for
immediate use) or offline (for use after complete initializations). I then
created a volume, performed mapping, and established read and write privileges.
A comprehensive context-sensitive help system guided me through
everything. Most people will have no trouble at all installing a storage array
of this class, but terminology varies from vendor to vendor, so it never hurts
to have good help when you need to clarify something.
There are two primary ways of configuring snapshots: AssuredSnap and
AssuredCopy.
AssuredSnap provides the 2722 with built-in volume snapshot capability
and performs SCW (single copy on write) operations on snapshot data to utilize
disk space more efficiently. Taking this further, AssuredCopy creates a full
volume copy (versus a logical volume copy with AssuredSnap) to protect against
virtual disk failure and eliminate application I/O bottlenecks.
Strong Performance
To assess performance, I ran Iometer 2006.07.27 to generate a number of
different workloads representative of a database/e-commerce environment, a mail
server environment, a streaming media environment and combinations of these
environments.
Throughput was consistently in the range of 350MB ps to 800MB ps, with
average latency in the 2- to 15-ms range. Performance peaked during the
streaming media workload, with a 3.37-ms average response time at a pretty
stellar 998MB-ps total throughput. Youll note that this throughput exceeds
4G-bps Fibre Channel, but its per controller. By running half the
Iometer load against Controller A and half against Controller B, I was able to
run some massive workloads.
Matthew D. Sarrel is executive director of Sarrel Group, an IT test lab
and editorial services and consulting firm in New
York.
Data Storage, Data Backup and Storage Virtualization 
/ 16 
