Copy Speed Test Results to USB 3.0 Drive w/ SSD - why so slow?

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chadwixk wrote:

I see how to quote you're entire reply, but I don't know how to break up the quote to then insert my replies...curious how if you don't mind...so bear with my formatting below to mimic this...well I could use the raw html editing, but that would take a while...and I'm assuming there is an easier way to do this how you did in your replies

 

You can delete stuff out of the quote, and you can quote more than once.  There are some situations where the forum software misbehaves - when that happens I work around the issue using the html model in the expanded toolbar.

One thing that can't be quoted is inserted code - </> in the toolbar.  Netgear changed the way that works a couple months ago, and introduced a bug.  ( Marc_V , JeraldM : it would be very nice if that was fixed!).

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chadwixk wrote:

I'm not a hardware or linux guy (more a microsoft web dev), so not sure if I'm interpreting these properly, but CPU and Mem or not at 100%, but maybe they are effectively at 100%, limiting throughput?

These numbers can be hard to interpret.  In your case, the load average is quite high (over 4).  That suggests that you are CPU bound.

• https://www.site24x7.com/blog/load-average-what-is-it-and-whats-the-best-load-average-for-your-linux-servers

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chadwixk wrote:

 

Thank you StephenB for your time in responding and helping me learn and investigate this.

This was in response to: 

ssh > cp: 18 MB/s

cp -r -u -v "/data/Videos/2022/12/2022-12-20-063917.mkv" "/media/USB_HDD_7/Videos/2022/12/"

 

Just curious why this one was surprising to you...because it was also ssh and 2.5x the speed of rsync?

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Surprisingly slow.

FWIW, I don't have a comparable NMVE drive to what you have.  My RN102 is for testing only, and has two 1 TB Seagate Ironwolf drives in it.  When I copy a ~1 GB file between two shares, I see

root@RN102:/data/Pictures# rsync -P /data/Videos/test.avi /data/Pictures
test.avi
    944,136,192 100%   20.34MB/s    0:00:44 (xfr#1, to-chk=0/1)
root@RN102:/data/Pictures#

and

root@RN102:/data/Pictures# rsync -P --checksum-choice="None" /data/Videos/test.avi /data/Pictures
test.avi
    944,136,192 100%   31.15MB/s    0:00:28 (xfr#1, to-chk=0/1)
root@RN102:/data/Pictures#

So noticeably faster with --checksum-choice.

cp is faster:

root@RN102:/data/Pictures# time cp /data/Videos/test.avi /data/Pictures

real    0m12.461s
user    0m0.030s
sys     0m7.330s
root@RN102:/data/Pictures#

Doing the math on the total times, I get 70 MB/sec for cp throughput.

Testing the read speed with cp, I see this

root@RN102:/data/Pictures# time cp /data/Videos/test.avi /dev/null

real    0m5.359s
user    0m0.020s
sys     0m3.400s
root@RN102:/data/Pictures#

Computed throughput here works out to about 160 MB/sec.  

FWIW, dd read speed depends on the block size:

root@RN102:/data/Pictures# time dd if=/data/Pictures/test.avi of=/dev/null
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 15.5109 s, 69.2 MB/s

real    0m15.536s
user    0m2.120s
sys     0m11.180s

root@RN102:/data/Pictures# time dd if=/data/Pictures/test.avi of=/dev/null bs=1M
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 5.7195 s, 188 MB/s

real    0m5.727s
user    0m0.040s
sys     0m3.920s

The first test uses a default block size (512 bytes), the second uses 1M. 

dd write speed similarly depends on block size (and is much slower for the 512 byte size).

root@RN102:/data/Pictures# time dd if=/dev/zero of=/data/Pictures/test.avi bs=512 count=2097152
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 82.2124 s, 13.1 MB/s

real    1m22.276s
user    0m2.610s
sys     1m9.120s
root@RN102:/data/Pictures#

root@RN102:/data/Pictures# time dd if=/dev/zero of=/data/Pictures/test.avi bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 9.21715 s, 116 MB/s

real    0m9.263s
user    0m0.030s
sys     0m5.700s
root@RN102:/data/Pictures#

I don't know what block size cp is using on the NAS, but I can approximately match the cp speed with a block size of 1M in dd. (Actually any block size over 128k gives me about 70 MB/s).

root@RN102:/data/Pictures# time dd if=/data/Videos/test.avi of=/data/Pictures/test.avi bs=1M
900+1 records in
900+1 records out
944136192 bytes (944 MB, 900 MiB) copied, 13.7353 s, 68.7 MB/s

real    0m13.744s
user    0m0.030s
sys     0m6.930s
root@RN102:/data/Pictures#

rsync appears to be using 128K (which is the max block size you can specify with -B).  But still much slower than cp (or dd).