Can Rockstor use SSD as cache?

[Dude (Keith)]

Can Rockstore use SSD as cache? And if so is there a good YT video on how to set up?

I have searched here and YT and have not found anything on Rockstore. Many other’s Synology and TrueNAS, Asustore, Qnas, etc.

I’ve used both TruNAS and openmediavault but have not set cacheing up on either.

Just sort of experimenting with Rockstore at the moment, I have a 9TB pool with multible disks and a spare 256GB SSD that is installed just idle at the moment.

[Hooverdan (Dan W.)]

@Dude, natively, Rockstor does not support a disk based RAID cache.

You will likely have to figure out a workaround to present a btrfs pool to the Rockstor WebUI using something like bcache. There are some scenarios described here (though it’s archlinux so you would have to adapt it to what openSUSE would require in terms of packages, etc.):

Bcache - ArchWiki

So, in any case, it will not be as straightforward as just “attaching” a cache to the RAID and then having btrfs take advantage of it, like it could be with other filesystems.

I assume you’re thinking about this more from a “what if” or do you see a particular need for your performance/management of the NAS?
If e.g. you were worried about transcoding with apps like Plex or Emby, then you can force the transcoding onto a standalone SSD, instead of a mechanical hard disk. Or when using the Rockon containers in general, you could put the Rockon root on the SSD as a standalone pool. Not sure how much improvement it would bring, though. But that might not be your main use case, especially since I think you’ve asked about a cache implementation for your RAID itself.

[Dude (Keith)]

Thanks for information.

I was actually just experimenting with RS, as the system is an old culled Intel-SV5000 dual Xeon’s 32GB ECC RAM and old pulled HD’s.

Have few old various size hard drives and ssd’s, no hardware RAID.

Might try the bcache, which I have used before with OMV and TrueNAS.

Will post comparisons if relavent.

[phillxnet (Philip Guyton)]

@Hooverdan & @Dude We do have a now old, from our CentOS days, developer reference for our bcache compatibility requirements regarding udev modifications written up in the following Wiki entry:

Bcache - developers notes

This document represents the current and pending state of bcache in Rockstor and is not an endorsement of it’s use or support status but is simply intended to share the progress and development made to date. It is intended as a developers document so any changes made should be in accordance with keeping this text up to date with the current code state, including in the case pending pr’s. If you wish to comment on bcache support in general, as opposed to the specifics of what is actually in play…

But ignore the “Building bcache“ section in the above as it should be available via an openSUSE package.

Back-then we did add the capability to recognise, and present within the Web-UI, bcache configured devices as indicated in the Wiki notes above. But we have no Web-UI capability to do the actual config - at least not yet. So that would all be a CLI thing. And potentially non-trivial if one is unfamiliar with such things.

What @Hooverdan stated re considering a pure ssd pool for application specific use, or part use, is way simpler than setting up an ssd bcache for other devices. Plus we have heard from very few folks actually trying bcache on Rockstor. So it is considered untested/unknown currently. But we should still recognise such devices once they are CLI configured.

Hope that helps.