ZFS checksum errors question

[Pestaninha]

Hi guys,

My boot device is currently a two USB stick mirror pool and last week I got a critical warning on the GUI telling me that one device had suffered an irreparable error. I did a zpool status on the shell and sure enough, one of the USB sticks was reporting checksum errors (and that was the affected pool).
I searched the forums and everything seemed to point to a hardware failure, so I replaced the disk.
The checksum error count was very small (13) and today I tried to read and write fully (used dd to read the stick to /dev/null and to write /dev/zero) to the usb stick without any issues. Furthermore, this is a fairly new stick which I bought for this purpose, it's a Sandisk Ultra, around a month and a half old.
Can anyone tell me what do the checksum errors mean? Should I have waited to see if the error counter incremented over the next few weeks/days?

Thank you

 

[fracai]

The quality of USB sticks covers a range from horrible to OK. I've experienced the same symptoms when I was using mirrored USB sticks. Think about what must have been going on before FreeNAS supported ZFS booting and we were all using a single stick.

The checksums mean FreeNAS tried to read or write the volume and there was an error. This could have been a momentary glitch or it could be dieing hardware. I have a box of likely perfectly good sticks that have cycled through my server because of these errors.

You can continue the dance of replacing USB sticks, but you'll be far happier if you can switch to a SATADOM or SSD.

 

[Arwen]

The quality of USB sticks covers a range from horrible to OK. I've experienced the same symptoms when I was using mirrored USB sticks. Think about what must have been going on before FreeNAS supported ZFS booting and we were all using a single stick.
...

Yes, I think some of the FreeNAS 9.2 and before problems were the USB flash drives. I would not run FreeNAS on a USB flash drive unless I mirrored good quality ones. And perhaps had a spare on standby.