Hardware Reference
In-Depth Information
allowing maximum performance. Motherboard-based RAID controllers almost exclusively use SATA
drives.
If you are considering a SATA RAID controller (or a motherboard with an integrated SATA RAID
controller), here are some things to look for:
• RAID levels supported. (Most support 0, 1, 5, and 10. A lack of RAID 5/6 or RAID 10 support
indicates a very low-end product.)
• Support for four, six, or eight drives.
• Support for 6Gbps SATA transfer rates.
• PCIe card with onboard controller (provides best performance and future compatibility; note
that low-cost PCIe cards are host-based and rely on the CPU).
Software RAID
Some operating systems include software-based RAID capability; in fact, limited RAID 0, 1, and
even RAID 5 functionality has been built in to some versions of Windows since Windows 2000.
When Microsoft released Windows Home Server in 2007 it greatly enhanced this capability with a
feature called Drive Extender, which allowed for the creation and arbitrary expansion of an array
using virtually any type of drive (SATA, PATA, USB, FireWire, etc.) in any capacity. Drive
Extender creates a virtual drive that is a combination of the assigned physical drives. There is limited
redundancy in that by default each file saved on a Drive Extender volume is automatically stored on
two different drives such that if one drive fails it can theoretically be replaced without losing any
data. If more than one drive fails, then data will be lost. Unfortunately, problems with Drive Extender
caused Microsoft to remove the feature from Windows Home Server 2011.
Microsoft has included a newer and better replacement for Drive Extender in Windows 8, which is
now called Storage Spaces. Just like Drive Extender, it allows you to build a virtual drive using an
array of drives of just about any type or capacity. One area where Storage Spaces differs from Drive
Extender is in the redundancy options. In addition to two-way redundancy where data is saved on two
drives, Storage Spaces allows for three-way redundancy, meaning that data will be saved on three
drives. This also means that up to two drives can fail in the array without losing data. While the
redundancy and reliability has been improved, just as with most software-based RAID, performance
falls dramatically as compared to either a physical drive or hardware-based RAID, especially in
write performance.
While the Storage Spaces feature in Windows 8 looks like an excellent option for a home server with
multiple data drives, just like any other RAID array, it doesn't replace the need for backup, meaning
you would need somewhere else to back up all of the data on the Storage Spaces virtual drive.
Normally, if you want both performance and reliability, you should look for hardware-based SATA
RAID controllers that support RAID Level 5 or 10, or an external storage device with built-in RAID
capability. You can install a PCIe-based RAID controller; however, many motherboards have RAID
capability built in via the motherboard chipset. Another option is external storage devices like the
Drobo (
www.drobo.com
), which can create and manage virtual drives using the various physical
drives mounted in the enclosure. Because they rely on dedicated management hardware, they can offer
better performance and reliability than even some hardware-based RAID setups.
