Schulz believes the external DAS products from the major server vendors are an overlooked treasure. “Look at Dell’s [PowerVault] MD1000 and MD3000 family. They sell a ton of them, they’re cheap, and a good value. You don’t get hundreds of terabytes, but you get good performance and RAID and everything else you need. Same from HP’s [StorageWorks] Modular Smart Arrays in the MSA2000 family. IBM doesn’t talk much about their [System Storage] DS3000 boxes because they sell themselves.”
SAS (serial-attached SCSI) has transformed DAS from boot disk to high-performance storage. “You can now get DAS external boxes that connect at 6Gbps. Two servers and one of those units, and you have a high-availability cluster that cost $200,000 not long ago,” says Schulz. “Companies getting into virtualization can drop 10 servers down to one and benefit from an external DAS box run by VMware.”
THINK LONG TERM
Reichman of Forrester Research warns resellers to think long term, even when the lure of lower-cost DAS is strong in the current economy. But while buying DAS in the past meant isolated storage, many applications are changing that model.
“Applications are doing more of the storage management chores, like replication and high availability, that used to need a SAN,” says Reichman. “Intelligence built into Microsoft Exchange 2010 can use a grid of X86 servers to get replication without the traditional SAN array. With applications like that, you don’t have to pay for storage systems and management intelligence. Oracle now does provisioning automatically from the Oracle DB, taking snapshots and using replication tools from within the database. This is moving intelligence from the storage layer to the application layer.”
As disk speeds and protocols improve, DAS can provide good enough performance for many small and midsize business situations. “A 2TB SATA drive is faster than a SCSI drive was a few years ago,” says Schulz. “And cheaper. Plug one into a USB 3.0 port, and it really rocks. External drives that use eSATA ports like the Seagate FreeAgent [GoFlex] run at 7200 RPM, have 32MB of RAM built in, and use 4GB of flash memory to improve performance. I use a drive like that to transfer large files, because it’s faster than sending them over the local network.”
Schulz offers a bit of sales advice for resellers: “When your competitor offers a SAN with all the bells and whistles because they’re trying to upsell and get all the budget possible, your job as a salesperson is to put barriers in their way, and remove barriers for your deal. Sure, you can offer a comparable Cadillac system, but in many cases you can also use DAS to get the same performance as a SAN for a much smaller budget.”
JAMES E. GASKIN is a freelance writer and former reseller based in Mesquite, Texas.
- DIRECT-ATTACHED means more than “internal” basic disk drives.
- APPLICATIONS ARE STARTING TO MANAGE STORAGE, so you may not have to.
- EXTERNAL DAS SYSTEMS can be shared among servers.
- USE DAS TO UNDERCUT COMPETITORS who propose a SAN for small server groups.
For More Information
DELL DIRECT-ATTACHED STORAGE Product options and specs.
HP MSA DISK ARRAYS Product descriptions and specs.
IBM SYSTEM STORAGE DS3000 SERIES Descriptions and product specs.
SCSI TRADE ASSOCIATION Serial-attached SCSI tutorials.
SERVER AND STORAGEIO GROUP Tips, FAQs, and articles.