HP has announced that its MSA1500cs, more formally the HP StorageWorks Modular Smart Array 1500, is the first storage array to support either SCSI or Serial ATA (SATA) disk enclosures behind a single controller shelf. It expects to offer both types behind the same controller shelf soon.

Hybrid cars can use either petrol or electric power depending upon road conditions. Such cars pollute less and use petrol while sat in traffic jams. Hybrid or dual-mode disk arrays employ the same idea.

The MSA1500cs can deal with up-to-eight attached SATA enclosures and provide up to 24 TB (using 96, 250GB SATA disk drives) of raw capacity. If the business needs SCSI reliability then attach up to four SCSI enclosures for a raw capacity of 8 TB (using 56, 146GB SCSI disks). HP's modular storage idea lets you use the same controller for either SCSI or SATA drives or both.

SATA drives are lower cost than SCSI drives and are useful, HP reckons, for "minimum I/O workloads such as reference data, archival and disk-to-disk backup". The SCSI disks are useful for more demanding I/O workloads, which need greater reliability.

Recently, HP also made a FATA - Fibre Attached Technology Adapted - drives announcement. Its EVA (Enterprise Virtual Array) 5000 can have either Fibre Channel disks or FATA drives in the same enclosure. It supports up to 35TB capacity with any combination of high performance (FC) and low-cost FATA drives using existing EVA enclosures.

Dual Purpose. Why?
One reason, the company says, is investment protection. Customers get more use out of their controllers. At the enterprise level customers can save money by using cheaper FATA drives for less critical data. We might suppose that where other suppliers would need two separate arrays to provide either Fibre Channel or SATA-type drives then HP can do it with one array. Similarly with SCSI and SATA. Customers may also save on floor space.

Ideally customers should have storage management software that helps them move data automatically across storage tiers. HP has a set of ILM - Information Management Lifecycle - offerings, both products and services. There is also an HP ILM partner program to generate ILM software products for HP kit.

This neatly fits into HP's Adaptive enterprise strategy with customers moving data as its value changes across a spectrum of storage tiers, from fast disk to archival media.

Who else is doing dual-mode drives?
No other supplier, other than HP, yet offers FATA drives. But the mixing and matching of FC and ATA or SCSI and SATA drives is becoming common.

EMC's Clariion CX arrays can have both SATA and FC drives in the same array. Its Clariion DL700 is an array positioned as a disk library replacement for a tape library, one to be used to backup faster Symmetrix arrays. We might envisage future products combining these various drive types and functions. The information lifecycle approach comes through loud and clear here.

HDS' modular Thunder 9500 V Series arrays can have both Fibre Channel and ATA drives, with the latter positioned for compliance, archiving and backup, for example, of HDS' enterprise Lightning arrays.

IBM's TotalStorage FAStT900 Storage Server can use either SATA or Fibre Channel drive enclosures. IBM says that it will be possible to have both types of enclosure in one FASt900 in the future.

The coming Serial-attached SCSI (SAS) drives can readily share SAS controllers with SATA drives and this could further popularise the idea of dual-mode arrays. Indeed we might even envisage triple mode arrays: FC, SAS, and SATA (or FATA). Information Lifecycle Management in a box as EMC, HP, IBM or StorageTek might say.