by James Pyles
Serial ATA (Advanced Technology Attachment), drives began arriving on retail shelves in November of 2002. They
use a completely new interface between the hard drive and the motherboard and
are quite likely to replace the standard ATA interface in the next few
So just what is the big deal about Serial ATA drives?
To answer that, we need to delve into a bit of history.
Since 1989, IDE drives have been the standard hard drive interface. Except for
enlarging the pipeline from 33 to 100/133 MB/sec with the invention of ATA
in 1998, nothing has changed about the interface between the HDD and the
motherboard. For almost 15 years (an eternity in the world of computer
technology), the standard connection between the hard drive and the motherboard
in PCs has been the same parallel interface.
So how is a Serial ATA drive different?
Serial ATA or SATA drives
are a new standard in HDD/motherboard interfaces and are touted as the next
mainstream storage interface. SATA drives are fast with the first generation
having a volume of 150 MB/sec compared to Parallel ATA (PATA) drive's 100
MB/sec. Generation two (coming out in 2005) is predicted to go up to 300
MB/sec. This is also better than USB interfaces at 60 MB/sec and generation two
will be better than current firewire volume of 200 MB/sec.
The current ATA drive's parallel interface will eventually
become a throughput bottleneck, especially as drive densities continue to
increase. In 2001, major vendors were able to put 40 GB of storage on a hard
drive per platter. By the end of 2003, it
will likely be 80 GB and future densities are predicted at 120 GB per platter.
This impacts throughput because the more density, the more pressure to
push data faster across the interface.
SATA interfaces can
make use of cables twice as long as IDE cabling at a full one meter. The cable
is thinner, .25 inches compared to a two inch IDE ribbon, and plugs into the
SATA drive in a manner similar to a network cable.
drives are also "hot swappable" meaning no more reboots, they are quiet
(thanks to fluid bearings), but not quite silent, use less power overall, and
come with either a 2 or 8 MB cache.
Now for the downside
Currently, SATA drives have not yet entered the
mainstream PC market. This is predicted to happen by 2004 when it is believed
that major vendors like Dell and HP will start offering SATA drives in their
upper end systems. If you want to use a SATA drive in your PC, you will not
only have to purchase the drive, power supply and cable, but a PCI SATA adapter
card. Your motherboard must also be SATA capable. For SATA to enter the
mainstream market, Intel will need to integrate this standard into their
chipset…planned by the middle or end of 2003.
The other downside: only one device can be used per port. This means that there is no
RAID capacity for generation one SATA since you can't run multiple drives on the
there's more. The SATA working group announced that SATA II will allow
additional ports to support up to 15 drives. This will benefit mostly servers
running multiple rack-mounted drives.
announced by the group are native command queuing, giving hard drives the
ability to prioritize data requests from multiple CPUs, doubling the bandwidth
from 1.5 to 3 GB/sec, fallover switches for when high reliability is vital, and
connections for external SATA II drives.
The speed and
increased throughput of SATA drives are extremely important in the future of
servers. While an end user is unlikely to notice the performance difference,
the speed improvement will be important in the use of RAID to operate multiple
Yeah, but how much does it cost?
I found a comparison of Maxtor SATA and PATA drives.
ExtremeTech published a comparison between Maxtor's DiamondMax Plus 9 PATA and
the Plus 9 SATA. Each drive has a formatted capacity of 200 GB, 66.67 per
platter and a rotational speed of 7200 RPM. The PATA drive will set you back
$210 USD while the equivalent SATA drive is a bit more at $275. Maxtor's SATA
FAQ states that SATA drives will be typically a bit more than equivalent PATAs,
throughout 2003 but as SATA drives become more common, the prices will reach
parity. The SATA Plus 9 currently comes in capacities of 60GB, 80GB, 120GB,
160GB, and 200GB.
Not trying to favor Maxtor, I went shopping
at Atacom.com for comparable Seagate drives and looked at the Seagate PATA 80GB
ST380021A versus the SATA Barracuda V 80GB. The PATA drive costs $83.95 while
the equivalent Barracuda ran $125.95.
What about drivers?
According to serialata.org, SATA supports legacy
drivers for PATA drives. In other words, you can install a SATA drive on a
motherboard with the appropriate PCI SATA adapter and use the OEM's existing
parallel ATA drivers. Vendors will begin supplying bridges for parallel to
serial conversion for legacy devices. This being said, Seagate's support page
recommends that, if your operating system (Windows 2000/XP in this case) doesn't
detect the SATA drive during installation, you may need to go to the vendor's
website to acquire additional drivers.
Although many newer motherboards have SATA controllers, not all do and obviously
older motherboards do not support SATA.
If you have a motherboard that does not support SATA, all is not lost.
You can buy extra SATA controller cards for between $20-$30 (US).
Silicon Image is
providing parallel to serial conversion for Linux. Their drivers are supplied
by the Linux ATA development site.
SATA and Linux
In June 2003, Pogo Linux included three new Linux
servers using Seagate SATA drives in its StorageWare line. They claim that
these servers are the first to use SATA for Linux. The StorageWare S140, S212,
and S316 are all powered by Intel Xeon processors with Hyper-Threading
The SATA drives are configured with a 3Ware
8500 Escalade SATA RAID controller in a RAID 5 array. According to Pogo Linux,
this will enable the StorageWare servers to give high speed performance at a
fraction of the cost of even the latest, high-end SCSI based servers. You might
want to save up your pennies if you're considering a purchase as the prices are
$3,499, $7,499, and 9,499 respectively for the above-listed servers. Pogo Linux
also produces the Velocity-DXWorkstation which comes with SATA, IDE, or SCSI
starting at $1,979.
None of this means you actually have to
spend thousands of dollars to use SATA with Linux. You will, at this point,
have to buy the drive, connectors, power supply and adapter and perhaps download
the drivers. For a few hundred dollars, you'll have all the materials to enter
the world of Serial ATA. Keep in mind that SATA drives are just now becoming
available in mass quantities and you will still have to wait until PC OEMs come
with SATA integrated. I mentioned above that this is predicted for 2004 but the
Maxtor SATA FAQ page was particularly evasive. It's likely that negotiations
between the major relevant vendors are, as of this writing, still in progress.
If you plan to use SATA and Linux on a home or small office
system, you will likely have to play around with the installation and
configuration. As with anything new, there is uncharted territory to explore.