In April 2016 I got an email from David Jao pointing out that USB pen drives have come a long way since 2010, which is when I last updated this page. In particular he pointed out you can now easily get large-capacity USB 3.0 pen drives that saturate the usable bandwidth of USB 2.0 ports.
As an example he mentioned a Sandisk Extreme 64GB:
"This thing flies! On my USB 2.0 thin client, I clocked it at 8MB/s random writes, which is faster than the included IDE DOM.
It might cost a little more than a proper SSD, but not as much as you expect (they make it up on volume). You don't need to mess with cables, or drill mounting holes in the case. You can even use the "secured" USB ports on the t5745 to keep the drive nice and tucked out of the way."
Not all pen drives are equal. This pages summarises my experience and will be
updated as and when I discover something new.
In checking out thin clients (at least those that will boot from USB) it's handy to have a number of pen drives set up with different operating systems. They are also useful for moving data to/from other systems. As a result I have collected a number of branded and unbranded drives of various sizes.
I bought a few 256MB unbranded drives - the plain red one in the picture above and some 1GB unbranded drives - the plain black one in the picture. The red ones work perfectly but I have grief with the black ones. Note however the black 1GB drives work perfectly with Windows XP/Windows 7 and Fedora Core 13.
What I think is the reason is evident if we look at the dmesg output when the devices are plugged in. (I plugged the 256MB pen drive first and then the 1GB one). The output shown below is from Fedora, but the DSL output carries the same information.
usb 1-7: New USB device found, idVendor=0204, idProduct=6025 usb 1-7: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-7: Product: Flash Disk usb 1-7: Manufacturer: USB usb 1-7: SerialNumber: 000000123456 ....... sd 4:0:0:0: [sdc] 501760 512-byte logical blocks: (256 MB/245 MiB) ....... ....... usb 1-2: New USB device found, idVendor=0204, idProduct=6025 usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 1-2: Product: Flash Disk usb 1-2: Manufacturer: CBM usb 1-2: SerialNumber: 30212000358B4903 ....... sd 5:0:0:0: [sdd] 521088 2048-byte logical blocks: (1.06 GB/1017 MiB) .......
The obvious difference is that the 1GB pen drive is apparently running with 2048 byte sectors rather than the more usual 512 byte sectors. This is what I believe is giving grief to the thin client boot code (will not boot) and to the drivers in DSL (will not mount the pen drive). To date I haven't been able to get these particular 1GB pen drives to work with DSL and a Neoware CA21.
If you think I'm wrong about the sector size being the problem please let me know.
The sector size is also reported by fdisk should you decide to try and repartition the device (as I did as part of my effort to try and sort things out).
So, if you're having problems with your particular pen drive, check the sector size. If it is not 512 bytes then I suggest you just put the pen drive on one side for use in more modern environments.
I also know of someone who was having problems and ended up using a Compact Flash card plugged into a USB/CF adaptor which worked perfectly.
I thought this would be simple - just use USB-Universal-installer.v1.7.9.exe from pendrivelinux.com. This was fine if I picked the in-built menu item of DSL.4.4.9, but pick "Try Some Other Live Linux ISO" then select the (previously downloaded) 50MB DSL-4.4.10 iso, and it complains that the 256MB flash drive is less than 700MB that it apparently needs and gives up!
Eventually I followed another link on the pendrivelinux.com website and downloaded "Linux Live USB Creator v2.5". This worked perfectly. The very extensive list of distributions that it has been tested with can be found here.
Having created a bootable pendrive I have found that they don't always work 100% of the time. Sometimes you need to swap the pen drive between USB sockets and/or power cycle the thin client before it will find and boot the pen drive.