USB Drives for OS... Why recommended?

[Binary Buddha]

So, I had a SanDisk Ultra Fit USB flash drive (SDCZ43-128G-A46 - 128GB) to run on Freenas off of. IMO this wouldn't qualify as one of the "cheap flash drives" people say to avoid.

However, I started getting CAM control errors and then wouldn't boot. After research, I found this is a known issue with running on flash drives as they're not "designed" for the amount of writes it was getting.

So question 1... What was writing to flash drive so much to cause it to fail in a little less than a year and how do I make it not do that?

question 2... If the writes are a known issue, why is it still recommended?

question 3... I'm currently running on an SSD due to the error right now. If I so choose, is there a "quick" way for me to migrate back over to an flash drive? I was thinking of doing a zfs snapshot send to the flash drive, but I don't know how that'll work with the bootloader and what not.

 

[SweetAndLow]

1. Nothing writes to the flash drive. You can put your system dataset in there but that's not the default.
2. USB are cheap and easy.
3. To migrate you reinstall and upload your configuration file.

Also remember people only complain when it breaks and not when it works. I have been using a crappy random USB stick for 2 years now and have had zero read errors.

 

[CraigD]

This is my guess

A very small amount of space is required for the OS, and few writes to the OS drive(s) config changes and logs...

One bonus of booting from a USB drive(s) is it frees up a port for another drive

Have Fun

 

[danb35]

To add to what's already been said, when that recommendation was initially made, the design of the FreeNAS system was very different. The boot device was a UFS filesystem, and the entire thing was loaded into a ramdisk on boot. It wasn't touched afterward unless you changed your configuration in some way. Also, at the time (think five years ago), SSDs were considerably more expensive. Now, it's a live ZFS pool. It mostly runs from RAM due to ZFS's caching, but the system doesn't use a ramdisk, and it's possible for more writes to touch the device.

 

[Mirfster]

SSD(s) FTW, cuz I have the extra ports to spare... :P

 

[danb35]

The other strike against SSDs is that they typically take a SATA port. Particularly with the X9 and X10 generation motherboards (and their associated chipsets), you usually had six SATA ports, which is a good number of drives for a RAIDZ2 pool. Needing to use one of those ports for your boot device wouldn't be as convenient. Sure, you can add an HBA, but that's extra expense that isn't generally needed in a small build.

Since the X11 boards have eight ports, this isn't going to be as much of an issue either going forward.