# SSD caching on X79 - two SSD are still required..



## Artas1984 (Oct 18, 2012)

I saw the reviews of Asus X79, in this case Deluxe (my friend bought one) and here is a clip about SSD cashing:

ASUS X79 - SSD Caching - YouTube

Clearly you have to have 2 SSD - one is the OS drive, and the other SSD you use as a cash for the HDD. In other words you can not use your OS SSD to cash your HDD, becasue we can clearly see that before chasing the SSD is being formatted...

1) Why on earth the reviewer did not mention this KEY fact?
2) How much capacity do you really need? If Seagate Momentus XT drives have 4 Gb of SSD inside them, is not that enough already? Why do you need support for SSD cashing over 64 Gb? That just does not make sense.


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## Albuquerque (Oct 18, 2012)

A few points.

Your first question was regarding the use of a single SSD for both OS boot and volume caching.  In the most simplistic sense, you are correct in that you cannot install the OS to the SSD first, then enable caching from that SSD to another volume. However, someone with a bit of computer savvy can install the OS to a spare spindle drive, engage the SSD cache for the secondary volume, and after that is complete use an imaging tool (Microsoft ImageX would work) to move the OS onto the remaining space on the SSD.  You now have your OS partition on that SSD, as well as the caching volume.

My second point addresses your question on caching size, but also dovetails nicely into your first question...  Why would you want 64GB of cache?  Why isn't 4GB (or 8GB) of cache enough in the Seagate Momentus XT drives?  Well, how many things do you want at SSD speeds?  As a lead-in to this, why would you really need to put the OS directly on the SSD partition, when instead you could simply let the caching software move it for you?

As you continue to use your machine, the caching algorithms will detect your most use disk blocks (not files, but block-level data) and move them into the SSD. Let's say your favorite games this month are Skyrim, BLOPS and WoW. How much data do those three games need to run correctly?  Is it 4GB?  8GB?  What if your OS is part of that cache?  And then three months from now, you're still playing WoW, but you've moved on to Dishonored and GTA-V.  How much disk space would you like to have in SSD cache _then?_

The reality is, you're not really approaching the SSD cache in the proper way.  This is meant to be a fire-and-forget system; don't spend your time trying to overengineer how the OS is stored by forcing it to SSD, instead let the caching system pick out exactly the blocks that need to be cached (ie the ones that are used most often - how much of the Windows OS files are truly used for boot? Here's a hint: far from all of them!) and then you can spend more time doing things that you _want_ to do with your PC.


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