Anyone have any advice on replacing cache drive?

[wayner]

I have been using unRAID for about 2.5 years and I haven't done much to my system recently so I have fallen out of practice.

I am using a SSD as my cache drive and it appears to be failing as it keeps giving me warnings that "raw read error rate (failing now) is 35160"

So I want to replace this drive with another. There are instructions for replacing your cache drive here: https://wiki.unraid.net/Replace_A_Cache_Drive

But they are convoluted as they involve removing everything from your cache drive to your array and then moving back to a new cache drive. Isn't there a way to install a new cache drive and move all files from old cache to new cache?

Either way - once I install the new cache drive and transfer all of the files should SageTV automatically restart and have everything running correctly from the new cache drive without having to do anything special configuration-wise?

[stuckless]

Originally Posted by wayner

I have been using unRAID for about 2.5 years and I haven't done much to my system recently so I have fallen out of practice.

I am using a SSD as my cache drive and it appears to be failing as it keeps giving me warnings that "raw read error rate (failing now) is 35160"

So I want to replace this drive with another. There are instructions for replacing your cache drive here: https://wiki.unraid.net/Replace_A_Cache_Drive

But they are convoluted as they involve removing everything from your cache drive to your array and then moving back to a new cache drive. Isn't there a way to install a new cache drive and move all files from old cache to new cache?

Either way - once I install the new cache drive and transfer all of the files should SageTV automatically restart and have everything running correctly from the new cache drive without having to do anything special configuration-wise?

I read through the instructions and they seem right. Basically configure unraid to NOT use a cache drive, then install the new cache drive, and then configure unraid to use a cache drive.

on many systems (mine included) the cache drive is not a normal drive in the array. It's a single drive and a process syncs the cache with the actual files in the array. If you install 2 cache drives you can actually make them work like the array where you can simply unplug one and then plug in another, but, most systems are not configured that way.

But if you follow the instructions, then yes, once you've done those steps, sagetv will just start and work without any additional configuration.

The reason cache disks behave differently is because their use is somewhat hidden from you. ie, when you request a file from a share, 'waynesfiles/filex.mp3' unraid checks the cache and then the array, but, you only ever request the location of the file on the array. So under the hood unraid makes decisions about where that file is located (cache or not). Because of that, files are duplicated on the cache drive and on the array, and because of that, when changing the cache drive, you want to make sure unraid simply isn't using the cache at all, then replace it, and then tell unraid to start using it again.

[wayner]

I think I am using the Cache drives in a similar manner to you - the only thing on my Cache drive is appdata, VMs (under the system folder), domains and an isos folder.

My settings are:

Share	Use Cache?   Comment
system	Prefer	     Dockers and libvirt.img
appdata	Only	     All appdata folders
domains	Prefer	     VMs?

Does this look right? I was having problems getting my ISOs files to move until I stopped my VM. I had an Ubuntu iso file there and a running Unbuntu VM and I guess that file is locked by the VM. I thought that it was only used to do the install of the VM, but it looks like I was wrong.

One other question - it looks my dockers have only been allocated 20GB of space. How do I allocate more? My cache drive is a 240GB drive and I never have used more than half of it.

Is there anything else I should have on my cache drive?

[stuckless]

I think for docker, if you stop/disable docker (in Settings -> Docker) you should be able to set a new (larger) size. I have mine set to 50g and I run 12 docker instances and I still have lots of space. Keep in mind the appdata is NOT stored in this 50g. This 50g is just for the container system and application files. Keep in mind that while you can easily make the drive larger you cannot shrink it, so I would avoid going 100mb, and just bump it it up a little at a time. I have a 50g docker.img and only using 20g right now.

To use the mover you need to stop all docker and VMs. (I think they mention that in their instructions).

In terms of what is right/wrong for the cache drive. That's entirely up to you. eg, I don't use cache drive for appdata. I thought about doing this, but, I've never needed to. I do have my 'sagemedia' share set to use cache 'yes'. I do this so that when recording multiple streams and watching streams the load is basically spread across multiple drives. ie, if I'm recording, I'm likely watching stuff that was recorded on the prev night, so reading the files is coming from the array, but the newly recorded files are put on the cache and then moved later (automatically). But again, there is not real right or wrong way to use the cache. It exists as a means for your to tune your system to get better performance.

[stuckless]

I should clarify as statement that I made in my first post. I said that I have a single cache drive, but, I actually have 2 ssd cache drives, and I did that for redundancy as well. So in my setup, if one drive failed, I could replace it easily. The cache pool uses brtfs (which I think helps with this and the fact that I'm using 2 drives that are not the same size).

Side note.. I had to replace a data drive in my array a few months back and I simply unplugged the dead drive and replaced it. I just told unRAID to use it, and it took it over and started to use it. No data loss and minimal downtime. I also added another 3TB drive a couple weeks to get more storage. So, for me, unRAID is already doing what it should do

[rerooks]

Yes, if you are just replacing a single drive in a multi drive cache, then just replace it and it will rebuild. Better to run mover first, though.

[glenner]

Wayner, when doing anything to my unraid server step 1 for me is to check if the "SpaceInvader One" guy has a youtube video up. In your case, you're in luck ("How to replace your cache drive"):

https://www.youtube.com/watch?v=ij8A...ndex=31&t=275s