Experience with a bad eSATA driver got me thinking: why do eSATA cards need drivers? After all, every PC out there already uses SATA with drivers built and supported by the OS vendor.
Thanks to an INTEL API called the Advanced Host Controller Interface (AHCI) it is now possible to buy driverless eSATA cards. Windows 7, Mac OS X, Windows Vista and some versions of Linux support AHCI.
How well does it work? I had to see for myself.
The goods I bought a MAXpower eSATA 6G PCI-e 2.0 controller card. This card has 2 6 Gb/sec external eSATA ports and is PCI-e 2.0 and 1.x compatible.
The unit is spec'd at 500 MB/s per port with PCI-e 2.0 or 250 MB/s total with PCI-e 1.x. Either is fast enough to handle uncompressed HD video if the storage can handle it.
The card is quite small, low-profile and less than 4 inches long. It easily plugged into my quad core Mac Pro.
The works I tried it with a SANS Digital 4 drive tower RAID and a Drobo S 5 drive USB/FW800/eSATA storage array. Even though eSATA isn't hot-swap like USB and FireWire, when the eSATA cable was plugged into each enclosure the drive mounted in a few seconds. w00t!
But it wasn't all joy: the SANS Digital box only showed a single drive. Turns out the MAXpower card doesn't support port-multiplier arrays - which most cheap multi-drive enclosures use. Some AHCI cards do.
The Drobo S didn't have that problem - it has a controller in front of the drives that virtualizes them - but the Drobo Dashboard app couldn't see the array, even though the Drobo was mounted on my desktop and functioning normally. Read and write, yes. Manage, no.
Data Robotics says they're looking at supporting the MAXpower card.
Even so, it is not a showstopper: once the Drobo is configured it doesn't need much watching. The lights on the front panel offer almost as much information as the Dashboard app (note: Drobo's Dashboard is not a widget on the Mac Dashboard, but an app named Dashboard).
Dashboard works fine with the USB or FireWire, but Drobo's built-in backup doesn't work unless it can see the array. Fine by me - I use Bombich Software's Carbon Copy Cloner for backups anyway.
Performance The Drobo S max'ed out at about 75 MB/sec - which may be due to the unsupported interface or maybe that's as fast as Drobo's go. I don't think the card is the bottleneck.
The Storage Bits take The good news is you don't have to rely on an overworked chip vendor engineer to create a robust and high performance driver. The OS vendor has already done that. But the cards are still new.
Driverless AHCI eSATA cards really work - on the system. The storage side isn't as clean. You need check to see if your existing eSATA devices will work.
In time more of these cards will be supported by more storage devices. But USB3 is coming up fast.
eSATA will have a performance advantage over USB3 for several years - the SATA drivers are much more mature - but for many of us convenience and cost will trump performance.
eSATA will be a useful but passing fad in home storage as USB3 catches up.
Comments welcome, of course. I bought the MAXpower card with my money online. I'm keeping it.