1

This is added 3 hours after the original post. I tried another flash drive. Sandisk 64 gb. Performance is resolved. Apparently the PNY drive labeled/marked as 3.0 is not equivalent to the Sandisk 64 gb device I tried later. Both devices had been purchased in the past 3 months. The one with bad performance had been used for a short time in a Roku TV. The Sandisk thumb drive is partitioned with an ext4 partition for Lubuntu and a swap partition. It works fine. I partitioned the PNY the same as the Sandisk and reinstalled. Performance with the PNY is still BAD

----------------- Start of original post/question -------------

Lubuntu 19.04. Installed from thumb drive (USB 3.0 32 gb Yumi UEFI) to USB 3.0 64 gb. Partitions are 200 mb fat32 (/boot/efi), 50 gb ext2 (/) and 8 gb fat32 mounts on /media , no swap. Test system is Core I5 gen 7, 16 gb memory. System boots and plays. Performance is intermittently sluggish and appears to be related to DISK I/O. When performance is bad the LED in/on the thumb drive is flashing constantly. Installed "iotop" and confirmed web browsers (firefox, chrome) do a lot more writing to the disk than I expect. Disabled "lxqt Power Management" because it appeared to be contributing to disk i/o.

My goal is to use the thumb drive as a portable dokuwiki/demonstration. I have installed apache, it works and am stumbling through the dokuwiki self-education process. Demonstrating dokuwiki with a web browser, booted from the thumb drive, appears problematic given that disk activity gets in the way of performance.

I am not using a casper-rw file system. Does anyone know that casper-rw does not exhibit similar disk i/o behavior.

Has anyone else seen this behavior on thumb drives? Should I use ext3 or ext4 for "/" and/or allocate a swap partition. Memory utilization never approaches the 16 gb of the test system, so I am assuming swap is not necessary.

Peeboo
  • 11

1 Answers1

0

What you're experiencing is related to the NAND technology underlying your USB stick and is unrelated to the USB standard.

The short answer:

All USB sticks are created equal but some are more equal than others! E.G. a USB 2 SLC stick is faster than a USB 3 QLC one.

The long answer:

The USB standard defines the connectors, cabling, power consumption and signalling and defines the maximum speed a device can work at.

The underlying NAND memory defines the minimum speed at which the USB stick works:

  • SLC: four times as reliable and four times as fast as QLC and four times as expansive to manufacture
  • MLC: half the speed and half the reliability of SLC but half the price
  • TLC: 1/3 the speed and 1/3 the reliability of SLC but 1/3 of the price
  • QLC: 1/4 the speed and 1/4 the reliability of SLC but 1/4 of the price

As you didn't mention any part numbers, I'm guessing that the SAN-Disk is using MLC and the PNY one is using QLC (SLC USB sticks are hard to come by nowadays and are not generally stocked and need to be ordered)

Community
  • 1
Fabby
  • 34,259