SM951 as OS boot device information

here's my Samsung 950 PRO M.2 NVMe

TimH wrote: Here are two Crystal Mark Runs in Win7 64x, first is a SSD Boot Samsung 840 250ish meg holding the OS. The second is two Samsung 951 256mb M2 cards RAID 0. Empty Not sure why the SSD is kicking the RAID 0's numbers so badly. Shouldn't it be the other way around?

No, and it's very simple why that is.

Benchmark tests first write data to the device being tested, and measure that speed while it is being written. Then they read back the data it just wrote to measure the read speed. That cycle repeats depending upon the type of test being done. Such as, large file (128K+) sequential, or small file (4K) "random", meaning small files in different locations on the drive, or "Q32" tests, meaning 32 IO requests in a line, sent to the drive one after the other, instead of just one IO request.

Your 840 EVO is in RAPID mode, which uses your PC's memory as a RAM cache for the SSD. If you checked the amount of memory being used by your PC about one minute after it boots, you would find at least 2GB being used by the RAPID cache. That memory now receives ALL data that is "written to" the Samsung SSD first, which is then later written to the SSD itself.

The data written to the RAPID cache stays there until enough new data is written to the Samsung RAPID cache to fill up the RAPID RAM cache, and the older data is written over by the new data. That is, unless the older data has not yet completely been actually written to the Samsung SSD, at its actual write speed capability.

When the benchmark runs on a Samsung SSD in RAPID mode, all its test data is written to and read from the RAPID RAM cache. So in reality you've just ran a benchmark on your PC's memory, not the 840 EVO at all. If you used some RAM disk software to create a RAM drive, and ran a benchmark test on it, you would get the same kind of results.

In reality, your 840 EVO cannot write a large file at over 5,000MB/s. It can write at ~500MB/s, which is what happens when the RAPID RAM cache actually copies the data to the 840 EVO.

All benchmark tests run on a Samsung SSD that is using RAPID are not testing the SSD itself, but just the RAM cache created by RAPID.

So your PC's DDR3 or DDR4 memory is faster than two PCIe SSDs in RAID 0, which is not a surprise. Turn off RAPID mode on your 840 EVO, and run the benchmark again to see the actual speed of that SSD.

You can't use RAPID with SSDs in RAID arrays. But if you could, you would again be just seeing the speed of your PC's memory and not the RAID 0 array itself.

I know of at least one website that compiles benchmark test scores, that includes RAPID RAM cache results as if they were the true speed of an SSD!   Truly embarrassing!

Anyone got different results? Or a similar setup to check against?

Curiosity got the best of me.  Microcenter had them in stock today so I grabbed the 250 gig version.  I started another thread and posted some quick benchmarks if you're curious.

Newegg has 11/1/15 as the availability date for the Samsung 950. Usually Microcenter is slower to stock new products than Newegg, hopefully this time that won't happen. My local Microcenter is my second home...

RAPID is no big deal IMO. It is a Windows process with a delayed startup, so not running when the PC boots. Benchmarks with RAPID are simply that of your memory, since it is a DRAM cache as you know.

The other reality about RAPID is while benchmarks show super fast write speeds, that is the DRAM cache. Any saved data must still be written to the SSD, which is done at the speed of the SSD of course. Nothing can change that.

The 850 EVO is the fastest SATA SSD in 4K/small file read speed performance, which makes it great for loading an OS. PCIe SSDs have better 4K performance, but there seems to be a limit to loading Windows, no less than three seconds from POST beep to desktop. Even my PCIe SSDs can't seem to reduce that time.

For many things, you won't see any difference with a PCIe SSD. But some things are faster. For example, doing backups or cloning to and from a PCIe SSD is truly faster.