StorageTek 9176
The StorageTek 9176 RAID disk subsystem provides two controllers, each with redundant connections to two 1Gbps Fibre Channel connectors for host connections and two pairs of redundant Fibre Channel arbitrated loops connected to the StorageTek 9170 disk arrays. I tested a unit that had two disk arrays populated with ten 36GB disks each. The StorageTek 9176 can scale to a capacity of 14.4TB using dual storage processors and 72GB disks. Usually a StorageTek engineer preconfigures the StorageTek 9176 before its installation, but I configured it myself to get a feel for the process. For each of the two processors, I first had to connect through a serial cable and configure the Ethernet interface. After each processor had an IP address, I performed management tasks and status monitoring by using StorageTek's SANtricity Storage Manager 8.0.
I installed SANtricity Storage Manager from the included CD-ROM, launched the program, and performed a device discovery. The discovery identified the StorageTek 9176 as a single storage array that owned both of the IP addresses I had given it. I double-clicked the storage array icon to launch the Array Management window, which provided a simple, intuitive means for managing and mapping the controllers, volumes, and disks within the array. After creating two RAID 5 volumes and assigning them to separate controllers, I attempted to perform LUN mapping but discovered the feature wasn't licensed. When you purchase premium features from StorageTek, you get a feature key that you use to enable the feature from SANtricity Storage Manager. I phoned the company and requested a key for SANshare Storage Partitioning, which enables LUN mapping. I received the key in my Inbox within minutes and enabled the feature. SANshare Storage Partitioning lets you group hosts logically, then designate which storage volumes those hosts have access to. I created Windows and UNIX groups and provided access to one volume for each group.
ATL M1500
The ATL M1500 is a 4U (7") rack-mountable modular automated tape library available with an optional integrated Prism FC310 Fibre Channel router for direct Fibre Channel connectivity. Each ATL M1500 module can contain two DLT or Linear Tape-Open (LTO) tape drives and 20 DLT or 24 LTO cartridges. The modular approach makes adding additional libraries easy, and you can stack up to 10 ATL M1500 modules as a single library by using Quantum's StackLink, which moves cartridges between the M1500 modules.
I implemented one ATL M1500 equipped with the FC310 router and two Super DLT (SDLT) tape drives alongside Datahogs' legacy tape library to increase throughput and capacity in the SAN environment. I ran the same test backups that I ran earlier, changing only the destination from the legacy gateway—attached tape library to the ATL M1500. Through performance gains from hardware upgrades, the throughput for a single-drive backup job was more than double the old library's throughput.
Choosing the Right Solution
I hope this glimpse of SAN technology has given you an idea of the capabilities and the hardware involved in building SANs. I took a somewhat backward approach by using equipment from such a disparate array of vendors. If possible, enlist the help of an integrator when evaluating, designing, and implementing your SAN. Many companies include integration services with the purchase of their product. Also, keep your SAN hardware as homogeneous as possible to limit the potential for incompatibilities and finger-pointing between vendors. Vendors are working on partnerships and alliances to ensure interoperability among products, so when you need storage from one vendor and connecting devices from another, you can choose a certified solution that vendor partners have thoroughly tested.
If cost is a factor and you have the technical ability to implement your own solution, look at QLogic's offerings, which offer a tremendous value proposition. On the other hand, if data is the foundation of your organization, you don't want to cut corners. When you purchase a more expensive solution such as those from Dot Hill, StorageTek, and Brocade, you're also paying for extensive support, qualification, and training services. The ADIC Gateway makes sense when you have a sizable investment in legacy storage and tape. If that's not the case, you might consider upgrading your tape library to something like the ATL M1500 when you implement a SAN to take advantage of the throughput gains that Fibre Channel and new tape technology offer.