High Water allocation question

[Darryn]

Hi All,

 

If I have an Unraid array with the following configuration:

Parity 3TB

Disk 1 2TB

Disk 2 500GB

 

What would the first High Water mark be:  1.5TB (3TB/2) or 1TB (2TB/2)?

 

ie.  I am trying to understand if the parity drive's capacity is part of the calculation.

 

Thank you.

[trurl]

Parity has no data so has no part in choosing which disk to write data to.

 

The first highwater would be at half the remaining space of the drive with the most remaining space. So disk1 has 2TB remaining, which is more than disk2 has remaining. Writes would go to disk1 until only 1TB remained on disk1.

 

The next highwater would be at half the remaining space of the drive with the most remaining space, so disk1 would still have 1TB remaining, which is more than disk2 has remaining. Writes would still go to disk1 until only 500GB remained on disk1.

 

[itimpi]

I did not think the highwater levels were based upon remaining space?    I always thought the levels were based on the size of the largest data drive, with each level being half the previous one.

[trurl]

17 minutes ago, itimpi said:

I did not think the highwater levels were based upon remaining space?    I always thought the levels were based on the size of the largest data drive, with each level being half the previous one.

Probably you are right. I don't usually worry about it. If you just leave everything on highwater it works itself out anyway. I haven't really bothered to figure out split level either since the wording was changed in the webUI. If you just let it split anything you usually will wind up with things staying together simply due to highwater. The most important setting of the three (and most often overlooked) is Minimum Free.