HardwareBanter - View Single Post - RAID disk "degraded" but divorced they are happy

**Paul** · September 20th 14, 07:27 PM posted to alt.comp.hardware.pc-homebuilt

wrote:
I have a PC setup with RAID1 by somebody else.
It has Asus P6T SE board with ICH10R.
Upon booting, the BIOS whinges that a disk is degraded, giving serial
number thereof. Then Windows also pops up a helful alert that disk on
port3 is degraded and that human should replace offending item.

Instead, I went into BIOS and changed SATA settings from RAID to IDE,
then ran Seagate disk toola on both disks. It says SMART is okay for
both, so I ran long diagnostic. Both disk pass.
So maybe I have intermittent fault, either drive or controller?
They have done 33000 hours, so perhaps time for a trade-in...

RAID is not a backup system.

Make a backup of the remaining healthy disk.

Then, you can attempt a rebuild if you want. The rebuild will clone
the good disk, to the bad disk (terminology applies to RAID1 mirror).

An array can degrade, if the timeout value for a disk, exceeds
the timeout for the hardware. This is where disks with TLER come
in. Some (more expensive for no good reason) WD disks, have the
recovery time truncated, so that a disk having trouble
reading a sector, won't exceed the response timeout value of
the RAID hardware and driver. Regular disks can take as long
as 15 seconds, when attempting to read a bad sector. The RAID
timeout is less than that. Perhaps a disk with TLER enabled
would be 5 seconds. Declaring an issue early, means fewer
attempts to recover the sector were made (which is bad), but
at least the array doesn't drop to degraded state unnecessarily
(which is good).

Paul