Cache drives not fully used

[Hastor]

I have a cache pool with two 500GB SSDs, default settings. So 1 500GB cache with redundancy. I have this set to a minimum free space of 150GB. I'm copying around 400GB, so I'd expect it to go to 350GB then switch to copying directly to the array drives.

However, it is currently at 194GB used, 306GB free, and has switched to moving files directly to the array drives, which is a bit slower with parity.

 

What am I missing? My share is set to a min of 300GB free space for the storage drives, and it is acting like it is closer to that, but still not quite hitting even that.

Apologies if it is something simple.

Attached diagnostics in case it is helpful. I appreciate any insight or pointing out of an obvious setting I missed!

My mover is scheduled for 10am so over 8 hours away, shouldn't have anything to do with it.

 

I'm using 16TB drives so I'd honestly like to keep 500GB free on each for their health, but it seems like if I do that, my cache drives would be useless. Does share free space override cache free space? If so, any way around that?

 

megachurch-diagnostics-20210518-0118.zip

Edited May 18, 2021 by Hastor

[JorgeB]

1 hour ago, Hastor said:

My share is set to a min of 300GB free space for the storage drives

This setting also applies to the cache drive when it's part of a share, the higher value of the two is the one which will kick in first.

[itimpi]

1 hour ago, JorgeB said:

This setting also applies to the cache drive when it's part of a share, the higher value of the two is the one which will kick in first.

I have seen other indications that this is the behaviour but I would think it is a bug and the two settings should be independent of each other?   Do you know if it has been reported as a bug?

 

 

[JorgeB]

5 minutes ago, itimpi said:

Do you know if it has been reported as a bug?

Always assumed this was the intended behavior.

 

[itimpi]

1 hour ago, JorgeB said:

Always assumed this was the intended behavior.

 

 

OK - I think I will raise it as a bug then and see what is the response.   If the settings are not independent then the size on the cache/pool will often be irrelevant.  I have seen no mention in the GUI help of this behaviour that I have seen and if it IS intended behaviour it should be mentioned there.

 

[Hastor]

Seems odd intended behavior. Well makes sense at a certain scale, but when you're using 16TB (hopefully bigger in the future) drives, it is reasonable that you'd want more free space on such a big drive, to keep it healthy, compared to the cache.

 

I believe this is all based on what your biggest file will be, but I want my 16TB to stop at say 500GB, but my biggest file will be 100GB so I should be able to set my cache to that minimum. This should consider drive health concerns and move to the next drive after hitting that minimum free space, while still allowing you to use your 400GB of cache on a 500GB drive....

 

In short, it should be considered that largest file size isn't the only factor when choosing free space on the storage drives, but it's the only big factor for cache, meaning cache should allow a smaller min free space.

 

Edit: For now, I've just set my free space on my storage drives to the same as the cache, but I really don't want my 16TB drives getting that full... I'd much rather it stops using a 16TB while it still has 500GB (or a little less due to the last file) free, but currently that would leave me with no cache.

Edited May 18, 2021 by Hastor

[doma_2345]

I think this is the same issue reported here