These are the current limitations with non-enterprise drives in hardware
RAID (especially with WD drives):

a) Time Limited Error
Recovery<http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery>
:

TLER is not enabled in all WD drives manufactured after 2010 (unless you pay
for "RAID Enabled" Enterprise level), so RAID out of the box is
problematic.  As a non-TLER HDD fills up with data, the error detection
firmware might take too long, and the RAID controller may drop that HDD from
a RAID array.  This timeout is typically around 10 seconds with Dell
integrated driver/host RAID solution.

Of course with WD drives we used to be able to get a utility (downloadable
from Western Digital site) to enable TLER so it works for hardware RAID.

WDTLER.EXE utility (originally developed by Western Digital, but
discontinued, yet still downloadable from some 3rd party sites) used to
allow for the enabling or disabling of the TLER parameter in the hard disk's
firmware settings allowing the user to determine the best setting for his
particular usage as either a stand-alone or RAID drive. This utility is
written for DOS <http://en.wikipedia.org/wiki/DOS> and a DOS bootable disk
is required with this utility to use it.

Western Digital now claims that using the WDTLER.EXE tool on newer drives
can damage the firmware and make the disk unusable. The WDTLER.EXE tool is
no longer available from Western Digital, and new disks will not be able to
have the TLER setting changed.

Most WD "Desktop class" disks cannot have the LTER setting changed as newer
drives; therefore will not provide stable RAID in Perc LSI drives.

b) SATA Desktop Drives are not Enterprise
Drives<http://forum.synology.com/wiki/index.php/Differences_between_an_Enterprise-Class_HDD_and_a_Desktop-Class_HDD>
:

For example, Western Digital enterprise
drives<http://en.wikipedia.org/wiki/Enterprise_disk_drive>such as
Raptor <http://en.wikipedia.org/wiki/Western_Digital_Raptor>, Caviar RE2 and
RE2-GP (RAID Edition) come with TLER Read "Enabled" (7 seconds) and TLER
Write "Disabled" (0 seconds) while desktop drives such as Caviar SE, SE16,
and GP come with TLER Read and Write Disabled (0 seconds).  Dell refers to
their Enterprise Drives as Tier1 and Tier2.

So, we know the risks, RAID failure, short lifetime, inability to rebuild
the RAID due to TLER off.
**
Is anyone successfully using basic (Desktop class, aka cheap) SATA drives
with hardware controller cards?

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