From owner-freebsd-questions@FreeBSD.ORG  Sat Jul 28 10:42:36 2012
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Date: Sat, 28 Jul 2012 12:42:34 +0200
From: Polytropon <freebsd@edvax.de>
To: Vladimir Videscu <vladimir.videscu@gmail.com>
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Subject: Re: FreeBSD on SSD
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On Sat, 28 Jul 2012 12:44:35 +0300, Vladimir Videscu wrote:
> Good day. I have recently bought a Seagate Momentus XT for my laptop.
> 
> The specs for the drive are :
> 
> RPM : 7200
> Buffer : 32 MB
> HDD Memory : 750 GB
> SSD Memory : 8 GB
> 
> 
> I wish to install FreeBSD on it, but I wanted to ask this beforehand :
> 
> Would it would be possible to install it on the 8 GB SSD sector ?
> Would it work, and how would FreeBSD generally handle the SSD share of the
> memory ?

I think you're misunderstanding what this drive basically is.
According to what I read from Seagate's web page, it is _not_
a combination of a HDD and a SSD where each part can be
addressed _independently_. The SSD component seems to
function as a kind of read cache, but it is controlled
by the disk unit's firmware itself. (I'm not even sure
it works without software drivers, judging by the funny
little pictures...)

http://www.seagate.com/internal-hard-drives/laptop-hard-drives/momentus-xt-hybrid/

http://www.seagate.com/internal-hard-drives/laptop-hard-drives/momentus-xt-hybrid/specs/

(manual see 3.2.2)

You could easily test it by attaching the drive to a FreeBSD
system and see if _one_ or _two_ disk devices (ad or ada)
appear.

If I'm wrong and it should really be "two units in one", your
idea would work. Install FreeBSD to the SSD part and apply the
known optimizations. Make use of the HDD part for OS components
that need much writes to prevent wearing the SSD.



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...