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Partial SSD cashing

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a b G Storage
December 14, 2011 1:39:25 AM

OK, so I have this ASRock motherboard that I am slowly growing into. I was originally looking into SSD cashing thinking I could get a nice big SSD (120 or 240GB), and use it as a cash for a RAID1 array with my 1TB HDDs. As I have been learning, this will not work as the SSD cashing uses the RAID functionality of the board, and the SSD cashing technology itself is limited to 60GB, which completely defeats the purpose of what I would like for it to do (cash all my programs and save files while having a single partition for all my discs, while having the redundancy of a RAID1).

So my 2nd thought is a little more exotic (as if the first idea wasnt crazy enough): Can I get a 120+GB SSD, partition it in half and use half as a system drive, and the other half as a good cash for a program/rendering drive? this way I could have Windows and a few select larger programs (like Adobe Premiere, Photoshop, etc) that I want consistent performance from on the SSD, and then I could put things like games, and other programs that I do not necessarily use all the time on the cashed HDD so I can fit a ton of space (500GB), and get a speed boost from the ones I use most often. Obviously I could accomplish this using 2 smaller SSDs, but I would prefer to buy one nice big fast SSD than 2 smaller ones in my rig.

If it wont work then I will plan on a large SSD for all programs, my current 500GB system drive would become MyDocuments, and then RAID0 for my 2 1TB drives for video editing projects, but not long term storage as RAID0 is not reliable (though they are getting old (3 and 5 years) and I should replace them when HDD prices come back down).
I am also planning a home server with a RAID 10 of 4 2TB drives to act as my backup, shared media (music, pics, and videos), and cold storage using Win Home Server. I already have a rack mounted HP workstation, complete with a P4 class Xeon and 2GB of DDR2 ECC ram all ready for it. It isnt much, but it should do just fine for 2 light users on a home network. I was just about to buy the drives for it when the flooding hit and I decided to spend the money upgrading my old c2Duo instead.

Will the new hairbrained idea work?
If not then does anyone have other ideas for my backup option?

More about : partial ssd cashing

a b G Storage
December 14, 2011 3:03:49 AM

update!
http://www.overclockers.com/forums/showthread.php?t=684...
looks like I had some misinformation, which in this case is a good thing.
1) SRT does not take the place of RAID, so I should have the option to RAID my HDDs, and then apply an SRT to it!
2) You can use an SSD partition as cash, and keep a 2nd partition for a dedicated OS drive! (Important because I have well over 120GB of programs, and I cannot afford a quality 240+GB SSD). So I can have the OS and a few select programs run directly from the SSD, and then have a fast 500GB SRT for my games, documents, and other stuff.

So now the plan is
c: 60-80GB SSD partition as a system drive with select programs (browsers, office, premiere, etc)
d: 40-60GB SSD partition as cash to a 500GB HDD (programs, downloads, documents, rendering/exporting, etc.)
e: RAID0 for 2 1TB HDDs for video editing (bulk audio and video footage for current projects, save final products to d: )

please feel free to let me know if I have any of this terribly wrong :) 
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a b G Storage
December 14, 2011 1:15:01 PM

A very curious setup indeed. Do you see any increased performance with this?

Also whilst pronounced the same it's cache not cash.
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a b G Storage
December 14, 2011 6:08:24 PM

I dont know yet. I am hoping to get the SSD for Christmas (but somehow I bet my baby is going to get all the good gifts this year lol). If not then I will get it this winter/spring whenever I have a little money and find a good deal on an OCZ or Crucial. What I have works, so I am in no hurry, but at the same time I spend a lot of time researching things before purchasing so that I know what to expect from what I buy (thus the sparkle graphics card that I would not have normally bought, and the 1333 ram instead of 1600 because it makes little to no difference with video, etc).
I find that I open a lot of the same documents over and over again when working on a project, so it may be in my best interest to have the CACHE (ty, I am a terrible speller) on the documents drive where I store my project files, artwork, music/audio, and other miscellaneous stuff rather than a single 'large' system drive. I know that the main programs I use, plus windows, only takes about 40-45GB so I can allocate 60+GB to that, and 60GB as cache. This way if I am playing a game or working on a project then I will get a little boost on those things while I am using them a lot, and then have it reallocated to something else when I start a different project. It may be a pain to set up, but it would be less maintenance in the long run if I am not having to uninstall/reinstall programs to make space on the SSD; Instead I will just let Intel take care of it for me :) 

With the SSD cache set as 'maximum' or whatever they call it where it acts as a write cache, I should get some nice performance exporting from the RAID to the SSD/HDD combo.

Currently I am set up with a 500GB system drive, 1TB documents/export/multipurpose drive, and 1TB video/project drive. It works, and I have used this method sense my old Pentium 3 real time video editor (you can export video faster reading from 1 drive and writing to another than you do with a single RAID1/0 drive). But with the new i7 I find the drives are just bottle-necking the system, so it is time to evolve into something a little better, and it is cheaper to do this than to have multiple RAID arrays.
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a b G Storage
December 15, 2011 10:36:35 AM

Oh I see.

Somewhat confused as to why you might configure it to be a write cache. The true performance improvement on the SSD is the read performance so I would have expected you to say read or both?
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a b G Storage
December 15, 2011 1:26:33 PM

you cannt (as far as I know) enable write cache only, enabling it just adds it to the read cache
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a b G Storage
December 15, 2011 3:35:31 PM

I've seen this setup a few times on the forums and it should help for your uses/situation but I've never actually seen benchmarks. The true performance improvement is access times. Although the new ssds will also have better read and writes vs hdds.

The caching only helps when reading the files. Enhanced and maximized modes are different ways to write the file on the ssd but it's when the file is on the ssd and the runs after that is when it will help. The rendered files will not go onto the ssd as only commonly used files get cached. However the video files and other program files being read to do the render is what is benefited.

BTW 1333 to 1600 is only $2-5 difference which is why 1600 is still recommended.
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a b G Storage
December 16, 2011 2:37:41 PM

thanks for the input k1114.
When I bought my 1333 it was a $50 difference for 16GB of ram, but I know that is not the case at the moment. When 8GB sticks drop in price I will likely go all out and get 1600. For the moment it was more important to get something working to finish some large projects, and I have been quite happy with it so far.

Maybe I will do some benchmarking before and after the SSD upgrade, and with the different cache/RAID modes to give people a reference point of what to expect in different configurations. I know it is difficult to find sites that review anything outside of the mainstream SSD+HDD because most people just play games and browse the web so throughput is not their largest concern most of the time. But for video editing I am sure it will be a big step up from where I am now.

My understanding is that enhanced mode offers a read cache only, and maximized offers both a read and write cache. Of course the write cache will be useless once it is full and everything must be spooled to the disc anyways (so maybe not so good for large video files), but one would imagine it would still help in day-to-day usage with documents and the like. Guess it is one more thing to consider.
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a b G Storage
December 17, 2011 3:45:21 AM

http://www.anandtech.com/show/4329/intel-z68-chipset-sm...
Quote:
Enhanced mode makes the SSD cache behave as a write through cache, where every write must hit both the SSD cache and hard drive before moving on. Whereas in maximized mode the SSD cache behaves more like a write back cache, where writes hit the SSD and are eventually written back to the hard drive but not immediately.

Enhanced mode is the most secure, but it limits the overall performance improvement you'll see as write performance will still be bound by the performance of your hard drive (or array). In enhanced mode, if you disconnect your SSD cache or the SSD dies, your system will continue to function normally. Note that you may still see an improvement in write performance vs. a non-cached hard drive because the SSD offloading read requests can free up your hard drive to better fulfill write requests.

Maximized mode offers the greatest performance benefit, however it also comes at the greatest risk. There's obviously the chance that you lose power before the SSD cache is able to commit writes to your hard drive. The bigger issue is that if something happens to your SSD cache, there's a chance you could lose data. To make matters worse, if your SSD cache dies and it was caching a bootable volume, your system will no longer boot. I suspect this situation is a bit overly cautious on Intel's part, but that's the functionality of the current version of Intel's 10.5 drivers.


I hope this clarifies the different modes. The benchmark also shows some synthetics comparing each mode.

As I said before the modes are just different ways to write files on the ssd: ie different types of write caching. Both are read caching as the files are read off of the ssd (the cache), that is how ssd caching improves performance.
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