IBM has announced a pair of entry-level workgroup disk arrays, including a scaled-down reincarnation of an iSCSI-based device that the company dropped two years ago.

IBM's new offerings include the iSCSI-based TotalStorage DS300, and the DS400 - a Fibre Channel array that scales up to 5.8TB and is priced between $5,000 and $7,000. Both arrays can be managed by IBM's ServeRAID tools and support remote data mirroring and copying functions. They're also the first new products to be sold under the DS brand name, which will eventually be extended to all of IBM's arrays.

The DS300 is a native iSCSI array similar to the 200i, which IBM first offered in 2001 and withdrew a year later after selling fewer than 500. The 200i was the first iSCSI array on the market - at the time, IBM said it was stopping development of iSCSI-based arrays and instead pursuing partnerships that would let its other products use the low-cost data-transport protocol via gateways.

When the 200i was introduced, "it really wasn't as cost-effective as it needed to be for the market space we were going after," said Cindy Grossman, IBM's director of storage marketing. "I think it was ahead of its time, frankly." But, she added, IBM's sales teams have been hearing more and more demand from users for a low-cost iSCSI array to consolidate data stored on Windows and Linux servers.

The DS300 is priced between $3,000 and $4,600 and can store up to 2TB of data, compared with the 3.5TB capacity that was offered on the 200i.

A network co-ordinator at a large insurance firm in California said that given a slowdown in IT spending at his company, iSCSI makes for a cheap alternative to Fibre Channel storage, as long as applications with high I/O rates aren't involved. "ISCSI isn't good for that because of the TCP/IP overhead and bottleneck caused by Ethernet," he said.

The network manager, who asked not to be named, said he has been using a 1.5TB iSCSI array for the past year to store data from three Compaq ProLiant servers. The systems were using about 90 percent of their internal storage space before the addition of the array, which cost about $25,000 and took one hour to install.

"It's proved to be dynamic," he said, describing one situation in which a server went down and IT staffers at the insurer were able to use Microsoft's iSCSI initiator driver to reconnect the array to another server and then attach it to the company's databases.

Enterprise Strategy Group estimates that there are about 1,500 iSCSI-based storage area networks now in use and that the number will exceed 2,000 by year's end. Tony Asaro, an analyst at the firm, said the use of iSCSI is quickly ramping up because of its cost-effectiveness. Users who adopt iSCSI don't have to invest in more expensive Fibre Channel disks, host bus adapters or switches, he said.

Asaro added that the number of iSCSI-based products offered by vendors has steadily increased over the past two years, helping to validate the technology for users.