On April 17, 2018 9:02:14 AM CDT, lsorense@csclub.uwaterloo.ca wrote:
On Tue, Apr 17, 2018 at 08:20:47AM -0400, Russell via talk wrote:
Currently I have two versions of the same os on the same machine. One on M.2 Xpoint nvram and one on a standard SSD. I'm playing around with tweaking before I do a final config. So far the Xpoint direct hw access appears 3x as fast as the SSD while real world throughput shows up about twice as fast on the Xpoint, recent INTEL cache fencing notwithstanding.
dd if=/dev/zero bs=1M count=1024 | md5sum 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.35008 s, 795 MB/s cd573cfaace07e7949bc0c46028904ff -
795 is just under twice as fast as writing to the conventional SSD.
That command didn't write anything to anywhere.
It wrote a bunch of zeros to a virtual file. Perhaps even touching a tmp file along the way. Even if it didnt touch tmp, it wrote the zeros someplace in order to perform the count. I was just trying to comment on the speeds of the two installs relative to the respective disks the OS runs from. I'm sorry you didn't understand that. Perhaps I should have said running the OS from the two different drives, irrespective of all the other disk writes which may happen when the OS operates normally when calling dd from a GUI.
It tests how fast md5sum can calculate the checksum of 1GB of zeroes.
Certainly in no way testing any disk speed. Reasonable test of CPU and ram speed perhaps.
Often tests provide side channel results which are not part of the expected normal metric but quantifiable data arises none the less. My appologies for the misunderstanding.
-- Len Sorensen
-- Russell