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I read from SO that memory is 100,000 faster than (mechanical) HDD in random access. But the answers there do not speak to SSD drives.
SSDs are different from HDD in construction. Does anyone know a rough estimate how much faster is RAM than SSD drives?
tinlyx
Posted 2017-01-31T19:02:08.943
Reputation: 1 126
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See https://www.quora.com/Is-the-speed-of-SSD-and-RAM-the-same:
Flash Memory is considerably slower than DRAM, and the way they are used by operating systems is very different.
A typical DRAM has a transfer rate of approximately 2-20GB/s, whereas typical SSDs have a transfer rate of 50MB-200MB/s. So it's one to two orders of magnitude slower.
Furthermore, the way it's used is very different. DRAM is far more flexible and is truly random access -- any word, any time. By comparison, flash writes have to erase an entire block at a time before writing to it; and there are other problems that need to be dealt with such as wear leveling and bad blocks.
wysiwyg
Posted 2017-01-31T19:02:08.943
Reputation: 2 313
4The new ssd's getting pretty fast one example is: Intel's new P3608 Series PCIe SSD, The drive has a sequential read/write speed of up to 5,000MBps (5Gbps) and 3,000MBps (3Gbps), respectively. – Simon Dragsbæk – 2018-07-19T07:50:34.620
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Run memtest86, it displays numbers indicating memory read/write speed.
FWIW an Intel Atom 330 based mini-computer I currently have standing here says "1927MB/s" for the main RAM. L1 Cache is 3748MB/s, L2 Cache is 3095MB/s, there is no L3 Cache.
These speeds will vary with CPU and computer design.
A google on "SSD disk speed" will tell you numbers to compare with; expect anything from speeds similar to fast HDD's (100-150MB/s, slow SSD) and up.
Hannu
Posted 2017-01-31T19:02:08.943
Reputation: 4 950
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DRAM is much faster than any SSD or other solid state storage device. Generally, you can put it to be at least 5-10 times faster, depending on frequency, generation and the SSD you are comparing it with. SRAM is even faster than DRAM, at least a few times more.
To get some sort of comparison, you can set up a RAMdisk on the target machine and then benchmark both the SSD and the RAM. You can get some information on this here:
http://www.pcworld.com/article/260918/how_to_supercharge_your_pc_with_a_ram_disk.html
PulseJet
Posted 2017-01-31T19:02:08.943
Reputation: 2 069
HDD speeds are currently up to 200MB/sec (sequantial), SSD speeds are up to 3200MB/sec. So in theory the difference would be up to 16x less. It is comparing apples to oranges though, SSDs act differently, so raw speed comparisions would be flawed. – Hennes – 2017-01-31T19:06:57.643
100.000 times faster is incorrect. Its a lot faster, yes, but 100.000 is an arbitrairy number. SSD disks are basically memory moduies in a harddisk container, though they are slower than actual memory in order to allow the costs to be lower. So they are still pretty fast. – LPChip – 2017-01-31T19:16:39.657
1Another prematurely closed question. Well done @LPChip and everyone else. Of course it's not opinion based. They have finite and measureable differences. This place is getting rather ugly from the web. Always landing here on great questions that have been closed. It just looks tacky – hmedia1 – 2019-11-06T18:51:53.393