[kwlug-disc] Interesting Tool -- pv

[Ron]

Alex Korobkin wrote on 2026-08-21 11:32:
> pv ./disk.img | dd of=/dev/sdb1

I saw that YSAP video William linked to and it reminded me I really 
should get in the habit of using it.


I did a test similar to the quoted line above and was surprised by the 
results - `pv` was *way* slower:

pv ~/Downloads/ISOs/neon-user-20250727-0745.iso | dd of=/dev/null
2.72GiB 0:00:30 [90.1MiB/s] [=================================>] 100%
5709824+0 records in
5709824+0 records out
2923429888 bytes (2.9 GB, 2.7 GiB) copied, 30.9357 s, 94.5 MB/s

dd if=~/Downloads/ISOs/neon-user-20250727-0745.iso  of=/dev/null
5709824+0 records in
5709824+0 records out
2923429888 bytes (2.9 GB, 2.7 GiB) copied, 1.17249 s, 2.5 GB/s


That makes no sense to me.

Oh, it's caching, a second try with `pv` shows it only slightly slower 
than `dd`: 2.3 GB/s vs 2.5 GB/s:

pv ~/Downloads/ISOs/neon-user-20250727-0745.iso | dd of=/dev/null
2.72GiB 0:00:01 [2.12GiB/s] [=================================>] 100%
5709824+0 records in
5709824+0 records out
2923429888 bytes (2.9 GB, 2.7 GiB) copied, 1.28682 s, 2.3 GB/s


New tool unlocked, if only I can remember to actually *use* it!

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