Re: md RAID with enterprise-class SATA or SAS drives

[Phil Turmel <philip@turmel.org>]

On 05/10/2012 05:15 PM, Stan Hoeppner wrote:
> On 5/10/2012 8:51 AM, Phil Turmel wrote:
> 
>> Hardware RAID cards usually offer battery-backed write cache, which is
>> very valuable in some applications.  I don't have a need for that kind
>> of performance, so I can't speak to the details.  (Is Stan H.
>> listening?)
> 
> Yes, I'm here to drop the hammer, and start a flame war. ;)  I've been
> lurking and trying to stay out of the fray, but you "keep dragging me
> back in!" --Michael Corleone

Mission Accomplished!  I am very interested in what professionals like
you recommend, even if I am not in a position to buy the pieces.

> I find the mere existence of this thread a bit comical, as with all
> others that have preceded it.  I made the comment on this list quite
> some time ago that md raid is mostly used by hobbyists, and took a lot
> of heat for that.  The existence of this thread adds ammunition to that
> argument.

I think it is just us hobbyists who suffer these problems, trying to get
the most out of our limited budgets.

At least we are brightening your day with comedy.

> If not for the fact Western Digital added "TLER" to the spec sheet of
> it's RE and Raptor series drives many years ago, nobody would have every
> mentioned it.
> 
> WD did this because those in the "channel" marketplace weren't buying
> the drives.  They saw no difference with these new "enterprise" drives
> but the much higher price.  WD has never sold RE/Raptor drives to
> server/storage OEMs.  WD has never had a presence in enterprise storage.
>  Seagate, Hitachi/IBM, Fujitsu, and to a small degree Toshiba, have
> owned that space for over a decade.
> 
> So in an attempt to drive sales, they added "TLER" to the sheet to
> differentiate from their desktop drives.  So what happens?  All the
> hobbyists immediately want to enable this "TLER" feature from the
> "enterprise" drives on their consumer models, because "TLER" is all that
> makes them "enterprise" drives, after all, "all WD drives are the same,
> just with different firmware, right?".
> 
> Proof point:  Few write about this subject using the generic term "ERC",
> which is used by Seagate, or the term Samsung uses, "CCTL".  Everyone
> seems to talk about "TLER".  Hmmm...  Coincidence?  No, marketing.

I won't argue with successful marketing.  More power to them.  Of
course, they aren't offering this in their more affordable products, so
me and my well-informed hobbyist compatriots won't be buying them
either.

I learned ERC before TLER, not that it matters much.

> You won't find a single discussion about ERC/TLER/CCTL on any enterprise
> storage forum, unless its brought up by someone desiring to cut cost
> corners using consumer drives.

Exactly.  But that doesn't provide evidence either way as to software
raid use in enterprises.

> So if md raid is not limited to use by hobbyists, and is indeed used in
> enterprise environments, then why aren't the enterprise boys discussing
> "the problems w/TLER and enterprise drives"?  Because obviously md raid
> has no issues when being used with enterprise (ERC/TLER/CCTL) drives.
> 
> Either that, or md raid is only used by hobbyists. ;)

Well, it is definitely used by us hobbyists.  :-)



Phil