HP announced its FATA, standing for Fibre Attached Technology Adapted, drives earlier this month. Techworld covered the announcement here and here. There is much to find out but more information is available to start building a fuller picture.

The HP message is that it is a good idea to give ATA drives a direct Fibre Channel interface because then they can fit straight into Fibre Channel disk arrays, such as HP's Storageworks Enterprise Virtual Array.

Then you can have fast, performance-centric SCSI-style drives in the same array as slower, capacity-centric ATA drives, which means that you can have online storage and nearline storage in the same cabinet. Suppliers such as StorageTek and EMC and IBM would supply two cabinets with different interfaces to accomplish this. The HP concept is more economical on floorspace and simpler, HP says, to manage.

SATA and FATA drives compared
The FATA drives are being developed with Seagate and a 250GB unit is promised in July. In sheer capacity terms this doesn't amount to much as Hitachi GST already has 300GB Ultra SCSI drive, spinning at 10,000rpm, and a 400GB SATA drive spinning at 7,200rpm.

HP offers Fibre Channel disks spinning at 15,000rpm with either 36 or 72GB capacity. These are therefore much faster, and much smaller, than SATA drives. Hitachi's largest SATA drive is over ten times more capacious than HP's smallest Fibre Channel disk and spins at half the speed

SATA drives currently have an I/O rate of 150MB/sec. The transfer rate will double to 300MB/sec with SATA-2, originally supposed to debut in the middle of this year. A third generation (SATA-3) would drive performance to 600MB/sec in the 2005/6 period as the technology developed. SATA-2 may not now appear until 2005 or 6. There is no firm date.

HP's FATA drives utilise a 2Gbit/s interface, which translates to 250MB/sec, half as fast again as SATA-1. If both ports can be used then perhaps 500MB/sec can be achieved.

It is expected that SATA drives will be used on desktop PCs as well as in drive arrays for servers. Their lack of enterprise-class reliability makes them unfit for 24x7 use and they are being built into secondary storage applications where constant access to the drives is not needed.

Content-addressable storage arrays, such as those from EMC and NetApp use these drives. Fixed content or reference storage arrays from StorageTek, such as BladeStore, also use them.

Enterprise array or entry-level server
Although HP is positioning FATA drives are being used in a nearline storage partition within an Enterprise Virtual Array, Seagate is not necessarily wholly on the same hymn sheet.

At the US Storage Networking World event, Seagate executives were reported as saying that FATA drives could be used for entry-level servers, calling FATA 'server-friendly Serial ATA.'

Mark Hamel of HP's advanced technology online storage division, posted a follow-up note to an FCIA meeting, saying, "There is no ATA to FC protocal conversion involved. The FATA disk drive is a native FC disk drive with all of the FC features and function(s) available." This suggests a more enterprise focus, Fibre Channel being expensive, than entry-level server use.

Reliability
HP is suggesting that FATA drives are more reliable than ordinary ATA drives because of dual-ported interfaces but that is not the problem. The ATA drive problem is that the drives fail. Amongst other things, SCSI drives have wider tracks and more robust components to increase reliability whilst enabling faster spin speeds.

Without the robust componentry needed for reliability, and the wider track size then FATA drives will fail at the same rate, more or less, as other ATA drives. It means that SATA arrays will need RAID technology to protect against such failure, and hot-plug technology to make their replacement simple.

It is suggested that the soon-to-announced Seagate FATA drive may be much more reliable than existing SATA drives, making it more suitable for server use

The price of FATA drives is said by HP to be half that of Fibre Channel drives. It is likely that HP's competitors will price their SATA arrays under HP FATA arrays. Since HP is the only FATA supplier, customers may demur at purchasing what they see as proprietary technology, even with dual sources of disk supply (Hitachi and Seagate.) The drives will be sold only by HP and branded as HP product.

The drives are basic ATA drives with a Fibre Channel interace and controller card fastened to them. HP says it has a copyright claim over the technology which puts it 12-18 months ahead of other vendors. Seagate and HP are open about working together on FATA technology. Hitachi admits to a relationship with HP but not to any working relationship focused on any particular product technology. This suggests that a formal HP-Hitachi FATA relationship doesn't actually exist yet.

FATA's future
Serial attached SCSI (SAS) drives are also coming. Therefore vendors wishing to provide both online and nearline drives in the same storage array will probably polarise into serial ATA and SAS-focused suppliers and all-Fibre Channel products. The SATA+SAS suppliers would need separate protocols and drivers for each type of drive. Just one interface and driver would, theoretically, be needed for a Fibre Channel product.

FATA's fortunes will be immeasurably enhanced if Maxtor, Western Digital and Hitachi GST do supply drives, and array vendors other than HP supply FATA arrays. Without these events ocurring then FATA is probably of practical interest only to existing users of HP Fibre Channel arrays.

FATA drives would also need to equal SATA drives in the capacity stakes, something at the moment they, or rather it, conspicuously fails to do.