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 Post subject: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 20th, 2018, 3:01 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
Hi All

I, like everyone, have a pile of buggered HDDs, spare SATA cables and open SATA ports.
So here the idea:
Repurpose the RAM caches on these HDDs (and SSDs with larger caches) as mini RAMdisks.
ie:
4x SATA3 HDD PCBs with 256 MB of RAM cache on them, RAID 0'd, would give one a ~1GB,
~2400MB/s RAMdisk..!?
These #s go way up with EOL M2/NVME SSDs like the 970 Pro with its 1GB cache if you have the slots for them.

Now that's a handy thing to have in any computer! Especially if combined with HDD/SSD caching software like PrimoCache etc.

So the question is:
How difficult would it be to mod the drive's firmware to be able to do this..??
I assume that depends on the various controler chips on drives?

I haven't yet combed through this forum for clues etc (will get to it), but am hoping for some feedback fro the 'gurus' here plz?


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 20th, 2018, 15:23 
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Joined: December 19th, 2006, 8:49
Posts: 10828
Location: Portugal
Logic wrote:
So the question is:
How difficult would it be to mod the drive's firmware to be able to do this..??


Near impossible.

If you were to spend years coding firmare, etc you could eventualy manage to access the RAM cache of the HDD PCB somehow and use it to store data but then what ? Whould you spend some more years on another diferent model ? By the time you did manage to get one or 2 PCBs to allow you to access the RAM to store data as a virtual RAM disk the capacity of that RAM and the time spent on the project would make this absurd and not viable/reliable.

Just buy some extra RAM modules and create a virtual RAM disk. Forget about that idea.

If you do want to do something with those damaged HDDs just sell them on eBay for parts or sell the PCBs for people needing them to attempt data recovery ...

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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 21st, 2018, 7:18 
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Joined: August 13th, 2016, 17:10
Posts: 98
Location: Vienna, Austria
This would be actually quite easy with the Samsung EVO840, they are supporting this out of the box. The only thing needed is that you open up the case, and connect the 2 SAFE-mode pins, since you want this permanently you could solder them together or bridge them with some conductive material. With the 250GB variant you get a 400 MB SATA disk that is directly representing the DRAM on the SSD. With the larger variants you might get more, I haven't tried that yet.
You can find more information about the EVO840 here:
http://www2.futureware.at/~philipp/ssd/ ... Manual.pdf


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 21st, 2018, 7:25 
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Joined: August 13th, 2016, 17:10
Posts: 98
Location: Vienna, Austria
I am wondering a bit why this should help more than just putting more RAM inside the PC itself and using that RAM for buffering. Could you explain your usecase a bit more, I am curious...
If you want more power loss prevention, there are variants like the PM853T which have several capacitors on them and even a lot of empty footprints on the PCB where you can easily solder on more capacitors for even more power loss protection. But if you are worried about power loss, perhaps a UPS system to supply the whole PC with power might be more interesting?


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 21st, 2018, 8:36 
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Joined: December 4th, 2012, 1:35
Posts: 3387
Location: Adelaide, Australia
I don't know if it benefits crypto miner rigs or password cracking rigs to do this but struggling to see any real need to do this. Interested in a use case if there is one though.


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 22nd, 2018, 9:49 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
Firstly:
Because its there! And we (possibly) can! :)
ie: We all have these potential RamDrives, so why not use them..?
Sure one could just buy more RAM, but where's the fun in that and these potential RAM Drives/Arrays are free..!

Use Case:
As read/write caches to speed up IO.
Especially the all important 4K random read/writes where even flash is slow (comparatively) and fast worn out.

Read:
A read cache that puts our RAM drive in 'RAID 0' with our system drive, but with a filter for the all important (to performance) small ~4K files.
ie: ~10 small, random 4K reads would happen in the time it normally takes for the drive to seek just 1...
This leaves the drive to get on with the large sequential it's faster at, at the same time as the 4K is read.
Readyboost does this and can be ...'persuaded' to work with SSDs.

Write:
A deferred write cache (yes UPS reqd) would allow for the writing and reading of oft used files, without them ever touching the SSD.
This would performance and improve and SSD life.
PrimoCache has this 'Deferred Write' functionality.
https://www.romexsoftware.com/en-us/pri ... ation.html

It would also be nice if write blocks equal to the write blocks of the SSD were organised in RAM before being written to SSDs, greatly speeding up writes and further improving SSD life.
The closest I downloadable solution I have found is a very beta filter driver called FlashPoint/OpenFlashFire:
https://www.romexsoftware.com/bbs2/en-u ... =35&t=4665

There is various other caching software I can list if anyone's interested.

As last resort one could always just use them as small pagefiles.
Windows will automatically use the least busy drive if multiple PageFiles are set up.
For this reason I have pagefiles set up at 1/2 the RAM cache size on all my (mostly idle) backup HDDs.
(It goes without saying that said HDDs have Buffer Flushing disabled and also have tiny partitions on the outermost/fastest tracks (exFAT, 64KB clusters) for said PageFiles)

In short; a free, fast caching tier between RAM and non volatile storage would be nice!

PS:
GpuRamDrive: GPU VRAM as RAMdisk:
https://www.romexsoftware.com/bbs2/en-u ... =35&t=4637


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 22nd, 2018, 9:58 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
Spildit wrote:
Near impossible.

If you were to spend years coding firmare, etc you could eventualy manage to access the RAM cache of the HDD PCB somehow and use it to store data but then what ? Whould you spend some more years on another diferent model ? By the time you did manage to get one or 2 PCBs to allow you to access the RAM to store data as a virtual RAM disk the capacity of that RAM and the time spent on the project would make this absurd and not viable/reliable.

Just buy some extra RAM modules and create a virtual RAM disk. Forget about that idea.

If you do want to do something with those damaged HDDs just sell them on eBay for parts or sell the PCBs for people needing them to attempt data recovery ...


I'm sorry to hear that Spildit.
Perhaps bridging the to spinner write 'wire to the read 'wire' (with some electronics?) is a solution to simplifying firmware modding?
ie: Anything 'written to disk' is immediately 'read' into the rea cache again..?


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 22nd, 2018, 10:02 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
sourcerer wrote:
This would be actually quite easy with the Samsung EVO840, they are supporting this out of the box. The only thing needed is that you open up the case, and connect the 2 SAFE-mode pins, since you want this permanently you could solder them together or bridge them with some conductive material. With the 250GB variant you get a 400 MB SATA disk that is directly representing the DRAM on the SSD. With the larger variants you might get more, I haven't tried that yet.
You can find more information about the EVO840 here:
http://www2.futureware.at/~philipp/ssd/ ... Manual.pdf


Wow!
Thx for the info sourcerer!

Perhaps other drives are similar and we just aren't yet aware of it.
Yet more research! Sigh! :)


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 22nd, 2018, 10:10 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
sourcerer wrote:
...If you want more power loss prevention, there are variants like the PM853T which have several capacitors on them and even a lot of empty footprints on the PCB where you can easily solder on more capacitors for even more power loss protection. But if you are worried about power loss, perhaps a UPS system to supply the whole PC with power might be more interesting?


I'm thinking a small PSU could be attached/soldered where those missing caps are to make persistent RamDrives that survive reboots and shutdowns.

Failing that; one could attach said psu to the conventional power plug.

I answered the Use Case questions in a seperate post,


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 Post subject: Re: Repurpose buggered SSD/HDD as RAMdisk/cache?
PostPosted: December 22nd, 2018, 16:16 
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Joined: December 20th, 2018, 2:33
Posts: 6
Location: South Africa
It seems my other replies and use case (IO caching) ether didn't post, or are awaiting admin approval?

I'll repost in a day or 2 if they don't appear?

Thx for the feedback everyone.


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