Clarification on SSD usage

[dgwharrison]

Hi All,

 

I've done a bit of reading and I think I've got it but I just want to make sure. I'm going to use 2 500GB SSDs, when I allocate them to the cache pool I'll get RAID1 and the whole lot will be used for write cache, I can't use them for anything other than the cache pool right?

 

So for example if I wanted plex to host it's media library on SSD, I would need a third SSD, is that right?  I can't say dedicate 200GB of the cache pool to the write cache and use the other 300GB for stuff like plex?

 

Assuming I'm right, and you can only use the SSDs in the cache pool as the write cache, wouldn't I be better to use the motherboard's RAID1 for performance rather than doing it in software?

[BomB191]

you can set a share to use the cache only. point plex to that and you'll get what you want. Why I'm not sure though plex reading from the array is just fine for several streams.

[dgwharrison]

2 hours ago, BomB191 said:

you can set a share to use the cache only. point plex to that and you'll get what you want. Why I'm not sure though plex reading from the array is just fine for several streams.

Thanks @BomB191, I assume I can address that from a docker volume using something like /unraid_sharename right?

 

The why is the loading of thumbs, fan art, posters etc. It's much faster from SSD when scrolling etc.

 

So can I mount a VM in a share on the cache as well?

[BomB191]

you can mount any share you like on the cache 

once your shares are sorted just point dockers/VMs to the correct share and you should be golden. No idea how to split plex to keep thumbs etc from the main media though. (It might even be kept in the app data so it would be on the cache drive anyway. but don't quote me on that)

[saarg]

Thumbs and all Metadata are in the appdata folder for plex. It's not stored with the media. This also makes the appdata for plex huge if you have some media. 

Set the default appdata share to use cache only and all docker containers will use the cache drive for appdata. 

 

The cache drive isn't only for write cache for the array. You can also create shares that only use the cache drive. 

[JonathanM]

12 hours ago, dgwharrison said:

wouldn't I be better to use the motherboard's RAID1 for performance rather than doing it in software?

Your basic premise has been well addressed in the other posts, but I wanted to clarify this specific point. Unless you have a hardware based RAID controller built in to your motherboard, which very few do, then a motherboard hosted RAID1 is software as well, and likely not supported in Unraid as it is driver based. The performance would be no better, even if the driver was available.

 

I've only seen hardware RAID controllers on a very few high end workstation and a few server boards. It's pretty uncommon, and the boards tend to be VERY pricey.

[dgwharrison]

8 hours ago, jonathanm said:

Your basic premise has been well addressed in the other posts, but I wanted to clarify this specific point. Unless you have a hardware based RAID controller built in to your motherboard, which very few do, then a motherboard hosted RAID1 is software as well, and likely not supported in Unraid as it is driver based. The performance would be no better, even if the driver was available.

 

I've only seen hardware RAID controllers on a very few high end workstation and a few server boards. It's pretty uncommon, and the boards tend to be VERY pricey.

Hi @jonathanm, yeah it is a xeon workstation based pc I've ordered, though I'm pretty sure it's only going to have intel rapid storage raid, which I assume would be supported but I take your point. From what I can tell not Every share has to have copy on write enabled anyway which I imagine increases the available space beyond RAID1 also, is that correct?