[GTALUG] Backups for files

D. Hugh Redelmeier hugh at mimosa.com
Thu Nov 5 13:05:41 UTC 2015


| From: o1bigtenor <o1bigtenor at gmail.com>

| A tip - - - some of the drives marketed as applicable to NAS raid arrays really
| aren't applicable. You need to be purchasing drives that have ERC or error
| recovery control. I was slapped upside the head because I had drives that didn't
| have that but when I bought the drives (early 2012) NOBODY was talking about
| that.

I've heard that some RAID systems do know how to deal with such
drives.  I haven't researched which ones.

Lots of us were talking about this (whining, actually).  I usually
called it TLER, Western Digital's term for it.  ERC is Seagate's name.
CCTL was used by Samsung and Hitachi.

Earlier it was possible to tell a drive to limit error recovery time.
Then the drive manufacturers locked this feature out on their cheap
drives.  Grrr.

Disks with TLER / ERC / CCTL & LCC [Table of drives] (2011 March)
<http://hardforum.com/showthread.php?t=1590200>

I posted to this list:
	From: D. Hugh Redelmeier <hugh at mimosa.com>
	To: tlug at ss.org
	Date: Thu, 28 Jun 2012 21:58:59 -0400 (EDT)
	Subject: Re: [TLUG]: 3TB Harddisk sale

	| From: Anthony de Boer <adb at adb.ca>

	| I expect I'll be trying the WD RE4 Lennart mentions next.

	My understanding is that RE and non-RE are the same EXCEPT for "TLER"
	(a trivial firmware difference).

	Without TLER, RAID won't work.  A drive will spend so much time
	recovering from a simple local error that the controller will declare
	the whole drive offline.  That is a big failure.  It generally
	requires the array to be rebuilt, possibly taking longer than the
	actual MTBF!

	That's how they do "market segmentation".  Market segmentation is a
	vendor's dream: sell essentially the same product at two different
	price points.

	If the drive manufacturing industry were not an oligopoly, this price
	differentiation would disappear.  In fact, I think Samsung's normal
	drives were capable of TLER; that's been fixed by Seagate taking them
	over.


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