New 9500S RAID controller builds on manageability, performance
If you’re familiar with SATA, you probably know that 3ware, an old-timer in that space, was recently acquired by Applied Micro Circuits (AMCC) and introduced a new version of its leading SATA RAID controller.
Like previous models, the 3ware 9500S comes in 4-, 8-, and 12-port configurations, but it promises to be much faster and to boast other improvements, such as extended RAID support, support for more host OSes, and improved management tools.
A SATA RAID controller such as the 9500, which is able to host up to 12 drives, requires a properly engineered enclosure. AMCC sent a 3U, dual-processor Advanced Industrial Computer (AIC) server with a 12-port 3ware 9500S controller and eight 250GB Maxtor drives installed.
The AIC server can accommodate 16 swappable 3.5-inch drives and still has room in the front for a diskette, a DVD drive, and a handful of controls. On the back, the unit hosts CPUs, PCI I/O slots, two GbE NICs, three redundant power supplies, and numerous cooling fans. It filled only two-thirds of the controller capacity, but that configuration gave me close to 2TB of nominal disk space.
Because of the number of drives mounted, I expected a clutter of connections — but inside the box I found just two cables neatly linking the controller to the drives area. In fact, my 3ware controller mounted MI (multilane internal), rather than plain, SATA connectors.
MIs are essentially InfiniBand connectors, each capable of transparently carrying signals and data of four SATA ports, which obviously cuts the number of cables and reduces the jumble inside the box dramatically. It’s a big help when deploying eight or more drives.
My box had Windows Server 2003 already installed on drives controlled by the 3ware card, but to get more flexibility and to measure performance more accurately, I reinstalled the OS on a separate, non-SATA drive.
After a quick install of 3DM2 (3ware Disk Management 2), the new version of the browser-based management software, I set the controller to RAID 5 on seven drives, leaving one spare for recovery. The 9500 offers all common RAID levels, including composite settings such as 10 and 50.
In addition to browser-based management, the controller has also boot-time and CLI administration, but I was able to create and remove RAID configurations online without ever needing to reboot and with little or no impact on existing LUNs (logical unit numbers).
3DM2 can set a schedule to execute some repetitive and time-intensive tasks, such as rebuilding or verifying a LUN during off hours. You can also run those maintenance tasks in parallel with normal activities and adjust the controller throttle to minimize disturbance to live jobs or to finish sooner. Rebuilding an array when a large SATA drive fails can take a very long time, which makes these controls useful in daily operations.
Nonetheless, speedy performance is the main motivator when choosing a RAID controller. AMCC’s documentation lists expected maximum transfer rates at 400MBps for reads and 100MBps for writes (measured with Iometer over RAID 5). It also indicates that CPU use shouldn’t exceed 3 percent during those tests.
It took me a few attempts to get numbers consistent with those published. After comparing notes with AMCC engineers, I replaced the Maxtor drives with eight WD740s, a speedy SATA drive from Western Digital.
I repeated the same Iometer runs on a RAID 5 array including all drives, this time measuring more than 400MBps on sequential reads of large buffers and over 110MBps on sequential writes — results very close to AMCC’s claims.
During those tests, Iometer tracked a CPU use slightly higher than the advertised percentage. However, my test box mounted a single 1GHz processor, whereas AMCC’s results were obtained on dual processor machines clocking 2GHz or faster, which explains the difference. This should be a yellow flag for your implementations: Pushing I/O speed to the max can steal CPU cycles from other apps on a server with slow processors.
I was quite impressed with the 3ware 9500. The controller comes at a reasonable price, is easy to set up and manage and, when installed in the proper enclosure, brings plenty of capacity and solid performance to a datacenter.
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