Jails on SSD: Y tho? Help me understand.

[Yorick]

This is a @pschatz100 thing. I'm wondering whether you can add to my rather incomplete knowledge of all things FreeNAS/TrueNAS.

Toshiba 128GB M.2 SSD for jails

Not the first time I've seen that. And I still don't get it. So you're giving up redundancy to gain ... what? Which jail needs so much I/O that the main data pool doesn't suffice?

I'm assuming there's a reason. I'm genuinely trying to understand. All my jails run on the main data pool and they seem to be extremely happy doing so. Granted that's a very short list: Plex, traefik, Foundry VTT x 2, Logitech Media Server.

So: Which jail(s) has/have such heavy I/O that it/they benefit(s) from being on an SSD? And is/are worth sticking it there despite losing redundancy?

 

[ornias]

In terms of power efficiency:
Hosting them on the pool means the pool also needs stay spinning to handle all small log writes and such.
Having a seperate mirror or single SSD is WAY more power efficient, certainly if you enable disk spindown.

Databases in a jail (something that isn't too crazy to host on the NAS itself), are a bit more IO bound.

 

[garm]

I’m doing it to stop my databases from fragmenting the #%* our of my slow mirror pool. And fragmentation is less of an issue on SSDs any way

 

[danb35]

Until the catastrophic failure of the SSD in question, I had my jails on a SSD. Since that failure, though, after briefly considering ordering another one and restoring from a snapshot, I just put them on my data pool. Why the difference? Well, way back in the near-forgotten past, there was such a thing as a VirtualBox jail. I had one of those with a few VMs set up, and figured the VM workload justified being on a SSD. Performance was pretty decent. But iX killed that (back in 9.3, IIRC), but my jails stayed there out of inertia. It did make it quicker to start up a jail, but not by a significant amount.

 

[garm]

I did start out with them on the regular spinning rust pool, but it was a noticeable boost in general performance of Nextcloud and some other web apps once I moved them to the mirror SSD pool (no loss of redundancy..)

 

[pschatz100]

This is a @pschatz100 thing. I'm wondering whether you can add to my rather incomplete knowledge of all things FreeNAS/TrueNAS.

Not the first time I've seen that. And I still don't get it. So you're giving up redundancy to gain ... what? Which jail needs so much I/O that the main data pool doesn't suffice?

I'm assuming there's a reason. I'm genuinely trying to understand. All my jails run on the main data pool and they seem to be extremely happy doing so. Granted that's a very short list: Plex, traefik, Foundry VTT x 2, Logitech Media Server.

So: Which jail(s) has/have such heavy I/O that it/they benefit(s) from being on an SSD? And is/are worth sticking it there despite losing redundancy?

Yes I have my jails on an SSD. However, I don't recall suggesting that there was a performance reason for this.

Back when jails were new to FreeNAS (yes, that long ago) I was constantly creating and destroying jails. Once, I accidentally deleted some data - so the next time I created jails, I put them on their own disk, which I could easily wipe and recreate at will. At the time, this made sense to me.

A few years later, I decided to boot from SSD. M.2 drives were just beginning to come down in price and I bought one as a boot device with the thought that it would save me a SATA port. Unfortunately, my system is not capable of booting from an m.2 drive, so down with that idea. What else could I use a small SSD for? As the disk that I was using for the jails back then was over 5 years old, I decided to replace it with the SSD. Since then, it has performed well for me so I have not been motivated to change it.

For the jails I have, there is no particular performance advantage.