Confused about cache [Performance and Space] (2x480GB -> 3x480GB)

[nka]

Hello,

I've tried to search arounds but can't find clear informations.

 

I currently got 2 x 480GB in my Cache pool. I got 480GB available.

According to "btrfs fi df /mnt/cache"  it's in "RAID1".

According to https://carfax.org.uk/btrfs-usage/ , 2 x 480GB RAID1 give 480GB of usable space.

 

Now, can I add another 480GB drive ?
If yes, Am-I right to thing I will have 720GB of available cache ?

If yes, will there be any performance lost ? I mean, if I had 3 x 480GB versus 2 x 360GB (I know they don't exist) for the same amount of space ?

 

Thanks a lot!

Edited January 14, 2020 by nka

[JorgeB]

6 minutes ago, nka said:

Now, can I add another 480GB drive ?
If yes, Am-I right to thing I will have 720GB of available cache ?

Yes.

 

6 minutes ago, nka said:

If yes, will there be any performance lost ? I mean, if I had 3 x 480GB versus 2 x 360GB (I know they don't exist) for the same amount of space ?

There won't be a performance loss compared to current config, 2 x 360GB would need to be used in raid0 to have the same capacity, and raid0 would be faster, but without redundancy.

[nka]

My bad... I mean 2 x 720GB.

But you answed my questions, thanks!