DDRamDisk: RAM disk, a disk based on RAM memory chips
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DDRamDisk: RAM disk, a disk based on RAM memory chips
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Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#2I don't have a use for this, but I enjoyed the detailed write-up!
In these days of fast SSDs, are there still uses for a RAM disk, beyond extreme niches?
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#3Not a new concept. Has been done a few times before. The use cases are very small, and getting smaller these days as motherboards accept larger and larger memory modules.
https://www.newegg.ca/gigabyte-gc-ramdisk-others/p/N82E16815...
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#4Fascinating read. The read/write performances are impressive. But the whole time I was reading the article I kept thinking... Imagine the performance of a ddr4... no, ddr5 ram!
I'd love to get my hands on one of these and try out a pxe booted os.
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#5I don't have a use for this, but I enjoyed the detailed write-up! In these days of fast SSDs, are there still uses for a RAM disk, beyond extreme niches?
SSDs have wear which will lead them to eventual failure. Wear land nearly as bad as a few years back, but you can still only write to a cell for only a limited amount of times. If you're constantly writing data to your disks, you may need something that doesn't die.
I would personally go with a "normal" RAM disk in this case, but CPUs only have a limited amount of RAM and memory channels available. Complex operations on RAM disks may also increase the load on the CPU which can be a performance downside if you're doing things like compiling large code bases. Coupled with a battery backup, this looks like a pretty neat solution to SSDs for write-heavy operations, assuming you persist the important data periodically on something else (such as a hard drive).
I'd be wary of bit flips running this card, though. Without ECC, bitflips in RAM are just something you should be expecting. Normal RAM doesn't operate with the same data for an entire year, but this semi-permanent setup may be more vulnerable to bitflips.
I know RAID cards will often contain a battery backed RAM cache for file operations in case the power goes out, perhaps this card can be useful for that as well? With ZFS you can set up all kinds of fancy buffering/cacheing and I imagine an SSD write cache would show wear and tear much faster than one of these cards, and you can't exactly hot swap M.2 cards. A couple of cheap gigabytes of persistent write cache may just be the solution some people have been looking for.
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#6Fascinating read. The read/write performances are impressive. But the whole time I was reading the article I kept thinking... Imagine the performance of a ddr4... no, ddr5 ram! I'd love to get my hands on one of these and try out a pxe booted os.
You have DDR4 memory or DDR5 memory as your normal RAM? Then you can make a RAMDisk using any number of software available on internet. And then you can test said drive using AS SSD Benchmark (same as the article's author).
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#7I don't have a use for this, but I enjoyed the detailed write-up! In these days of fast SSDs, are there still uses for a RAM disk, beyond extreme niches?
A very useful use case discovered no later than last week : local dedup management by Synology C2 Backup Agent and TBW on the OS SSD.
C2 Backup agent stores dedup/chunks data by default in ProgramData, which is stored on C:... which is usually a SSD nowadays.
I noticed a 3:4 ratio between written data in local dedup folder vs uploaded data volume on the remote C2 5 TB storage (suscribed a C2 Business).
TBW grew indeed horrifyingly fast on the SSD, and I estimated it would completely wear it in about a year or so, with the 2 TB and growing data to backup with my standard retention scheme.
So I made a 32 GB (16 GB was not enough peak size) lmDisk ramdisk with backup/restore at shutdown/startup (it is featured by lmDisk and quite nicely), mounted in place of the dedup folder, and ran my tasks.
poof, reduced TBW on SSD by 99%.
(4x16 GB DDR4 ECC Reg on my server, so not concerned about memory errors)
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#8Not a new concept. Has been done a few times before. The use cases are very small, and getting smaller these days as motherboards accept larger and larger memory modules. https://www.newegg.ca/gigabyte-gc-ramdisk-others/p/N82E16815...
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#9When doing my PhD around 2004 I was running simulations with Fortran programs to do optimizations. A genetic algorithm would call the Fortran program and change the parameters by creating input files and reading output files.
I found out that disk access was the bottleneck of the optimisations. So I used a RAM disk software to create a disk-drive in RAM. It increased the simulation speed by orders of magnitude.
Re: DDRamDisk: RAM disk, a disk based on RAM memory chips
#10Fascinating read. The read/write performances are impressive. But the whole time I was reading the article I kept thinking... Imagine the performance of a ddr4... no, ddr5 ram! I'd love to get my hands on one of these and try out a pxe booted os.
There's a blog post about their DDR4 version from last month. Sustained read and write speeds of 15GB/s for sequential operations, with about 3GB/s for random I/O seem to be the expected throughput.
I don't know what loads demand such high persistent throughputs, but that's one place SSDs still can't compete, as performance quickly drops when their DRAM cache fills up.
Still, NVMe drives to up to 10GB/s these days, I think we're close to reaching a point where the PCIe overhead towards these RAM drives will soon make them unable to compete with persistent storage for performance. Preventing wear will be the only reason to go for these RAM drives.
If you want to try to experience the performance of a RAM based PCIe computer, there's very little preventing you from dedicating a portion or RAM to a RAM disk, copying your boot image to that, and running directly from RAM. Several Linux recovery images are built to do exactly that, in fact. If you want to run Windows or something else that doesn't have such functionality out of the box, I imagine using a lightweight Linux VM to bootstrap (and forward) your OS peripherals may solve that problem for you as well.