SSD balancer question

[dslabbekoorn]

I am looking to put a 2tb Nvme drive in an adapter (16x PciE) in my server (44tb spread across 16 spinner HDD's) and divide the drive into 2 partitions.  I want to use them as landing pads for the SSD Balancer to use and I'm totally new to using this setup.  Any advice and help would be appreciated. I know the balancer needs 2 "drives" to work at maximum speed and this should speed up the server in general since a 1tb landing pad can hold a lot of data before needing to flush to the archive HDD's.  My system drive is a Samsung 980 SATA SSD already so I would gain nothing trying to put it on the NvMe.  My Media Server is built for comfort not for speed, it's just an Intel I5 with 32gb ram but it gets the job done local and online.  Sorry for rambling on and again TIA for any help setting this up.  Dave

[Christopher (Drashna)]

If you don't mind a more complicated setup, you can get away with one drive for SSD Optimizer. 

Namely, add all of the regular drives to a pool.  Then add that pool, and the SSD Optimizer to a (separate) pool.  Enable duplication on the underlying pool, but not on the top level pool, and enable the SSD Optimizer just on the top level pool.

[dslabbekoorn]

Thanks, but I'm hoping to just add either two 512Gb  nvme drives in one or two adapters or one 2tb nvme drive partitioned into two 1tb "disks" if I can do that.  That way both disks used would be equal in size and speed.  I've just been reading many posts on this and they seem to be saying that the SSD balancer needs two physical disks (not two partitions) on the same disk to work.  I'd love to be wrong about this (it would be cheaper & easier) but I have nvme adapter and drives to cover two separate physical disks and I would think the drives at 512Gb each would be large enough to function as a landing pad/cache for the spinner disk pool.  Can I do it normally on one physical disk (partitioned into two 1tb "drives") or do I need to use two separate drives?

[Shane]

For real-time duplication you need two separate physical disks, if your disks have multiple partitions it will still pick partitions on separate disks; the SSD Optimizer reflects this in how it treats multiple partitions on a single disk as a collective entry.

So If you're wanting to keep it simple with one pool and 2x real-time duplication you'd need 2 physical SSDs to avoid immediate writes to your HDDs.

If you have only 1 physical SSD you'd need to either use Christopher's suggestion above, or turn off real-time duplication and let the pool duplicate at night, to avoid immediate writes to your HDDs.

[dslabbekoorn]

Ah, so it does require two physical drives.  I can do that. Is this just a quirk in Drivepool or something more basic in the machinery?  What basic settings would you recommend I start with?  The nvme SSD's will be 512Gb each, my OS is on it's own SATA SSD with my 60Tb of archive drives behind everything in several enclosures.  I've never done this before and find the possible benefits worth the effort.

[servonix]

The requirement for two physical drives (or rather as many physical drives as the duplication level of folders to avoid also writing to hard drives with realtime duplication enabled) is to prevent all copies of data from being stored on only one SSD.

If both copies of data are written to two separate partitions of a single SSD and that SSD were to fail before the data is moved to hard drives then you would lose both copies of the data.

As for recommended settings, the defaults are mostly fine IMO. You may need to tweak the balancing settings though if you want data moved over to the hard drives quicker or if you want file placement rules to keep some files/folders on the SSD's and not have them moved over to the hard drives.

[dslabbekoorn]

OK, even Homer gets it now.  Thanks to all for educating the noob.

 

[dslabbekoorn]

Well now, courtesy of a surprise eBay win, I now have my choice of two 512Gb NvMe  drives or two 1Tb NvMe drives to use as my SSD landing pad for the pool (73 Tb of spinners)  Which one would be more beneficial to the pool?  I was thinking of having the SSD's flush to the pool at 70% of capacity.  I guess I'm asking if the additional size of the cache would be worth dedicating the bigger drives to it or stay with the 512Gb drives.  Any advise?

[Christopher (Drashna)]

That really depends on the size of files you typically add, and how much data you may dump at once.    In general, the 2x 512Gb drives should be more than plenty for most anything you'd throw at it.   Though, if you wanted to use file placement rules to keep data on there, it still depends ... 

My personal opinion?  512Gb for the cache, and 1TB drives for the gaming PC.