I personally do not trust the USB Drive.

However unRaid files are saved on the USB Drive. 

If the USB drive go bad, i assume whole system will down.

i'd like to plug in second USB for backup for OS.

Is there any built-in function that support my idea?

Actually, the OS does not run on the USB drive. The OS runs in RAM. It is unpacked fresh at each boot from the archives on the USB drive into RAM, and all of the usual OS files are actually read and written to RAM.

 

After boot, some settings that you have made in the webUI are also read from the USB drive into RAM. And of course, if you make any settings in the webUI, these are written to the USB drive so they can be read on the next boot. Other than that, the USB drive is accessed very little.

 

You can always download a backup of your USB drive by going to Main - Boot Device - Flash and pressing the Flash backup button.

 

 

Most of the long-time users here will confirm the longevity of their USB device in unRAID. My oldest system is nearly 10 years old and still running with the original USB stick.

As @trurl explained the OS runs in RAM memory, it is mandatory that the USB device stays plugged in while the system is operational, but usage of the USB device itself is kept to a minimum.

 

Like any high profile system you rely on... BACKUPS are key.

 

Data on the disks (other than cache) are protected by parity. Backing up other things like VM XMLs, Docker templates, DockerAppData, PluginData, etc, can easily be automated by plugins.

On top of that, I have screenshots printed out of which drives are in which 'slots' in the UI, so i can make sure everything is the same if I needed to start from scratch and didn't have access to any data on my drives (in case of a USB failure). 

 

I'm pretty confident i could be back up and running as-is without any issues within an hour if my USB drive decided to give up. 

Edited May 25, 20188 yr by billington.mark
words

I absolutely hate that unraid boots off USB into ram. I’m replacing the USB stick yearly and when things start to go wrong, it’s a complete melt down on unraids part. Shares stop working, static ips change, dockers start corrupting and so on. I’ve replaced ram to make sure it wasn’t that, but always leads back to the USB. 

Most do not have these problems. I have been using the same Flash for 6 years. 

 

Are you using USB2 Flash and USB2 port?

21 minutes ago, homelessdorito said:

I’m replacing the USB stick yearly and when things start to go wrong

Definitely not the general experience and majority of users have no issues at all.

You may want to reconsider the type of USB stick you are using and its placement (heat is a common theme)

On 5/23/2018 at 4:49 PM, trurl said:

Actually, the OS does not run on the USB drive. The OS runs in RAM. It is unpacked fresh at each boot from the archives on the USB drive into RAM, and all of the usual OS files are actually read and written to RAM.

Perhaps a better way to think of it is that the Flash(/Boot) Drive is equivalent to a Windows installation disk.  However as the user sets up Unraid (initially  and sequentially), the setup parameters are backed up by writing them on the Flash Drive.   Thus, on subsequent restarts, after the OS install is completed, it will load those setup parameter files to finish setting the server to its previous state. 

8 minutes ago, Frank1940 said:

Perhaps a better way to think of it is that the Flash(/Boot) Drive is equivalent to a Windows installation disk.  However as the user sets up Unraid (initially  and sequentially), the setup parameters are backed up by writing them on the Flash Drive.   Thus, on subsequent restarts, after the OS install is completed, it will load those setup parameter files to finish setting the server to its previous state. 

I think of the archives on flash as the firmware. Then, as you say, there are additional settings stored on flash so they can be reapplied at boot. But those settings are themselves loaded into RAM for reading, and get written to flash if they are changed so they can be reapplied at boot, etc.

 

Possibly there are some details that deviate from this model, and I know other things such as some plugins will write to flash. There has been ongoing discussions to limit writes to flash.

My 2GB Cruzer has been kicking strong for the last 9-10 years. 

 

With all the changes to unRAID over the years, files accessed off the USB has dropped dramatically. It more or less loads the OS off the USB into ram and then your USB just sits there nearly in an idle state until you reboot it again. 

20 hours ago, homelessdorito said:

I’m replacing the USB stick yearly...

The only conclusion I can reach is that you're doing something wrong, or your USB device is maybe cooking.  Some USB 3.0 sticks run far hotter than needed.  For the occasional access that Unraid requires, USB 2.0 is perfectly OK.  Like many others on the forum, my sticks are years old (in use since early 2011 in my case) and no signs of issues.  

Edited December 20, 20196 yr by S80_UK

21 hours ago, homelessdorito said:

I absolutely hate that unraid boots off USB into ram. I’m replacing the USB stick yearly and when things start to go wrong, 

You really need to stop your cat from sabotaging your server. That or you have some sort of electrical fault issue with your power, power supply, motherboard, and/or usb ports.

 

I'm still using my original USB stick from a decade ago.

FWIW- Last weekend I was troubleshooting an issue so I had to un-rack my server, and through sheer laziness left the USB thumb-drive hanging off the back. While re-racking, it snapped off....

 

I was back up in less than 20 minutes from download to re-installation.

On 5/24/2018 at 8:35 AM, bonienl said:

Most of the long-time users here will confirm the longevity of their USB device in unRAID. My oldest system is nearly 10 years old and still running with the original USB stick.

As @trurl explained the OS runs in RAM memory, it is mandatory that the USB device stays plugged in while the system is operational, but usage of the USB device itself is kept to a minimum.

 

Well today already a 2nd USB drive failed, that is became read-only, both within 2 years in two different systems, and this one a proper Patriot TAB 16GB in a brand new system, only in use for 5 months! Already tried diskpart and EaseUS tool, to no avail. The first time I read about a script in the go file so that you can boot from a 2nd USB, with the original USB only there to read the OS-key from. At that time I didn't think much use, but now I really would like to set this up - if UNRAID cannot fix this?!