hello everyone, thank you for taking the time.
i have two options:
1 nvme of 4T
2 nvme of 2T (cost:+50€)
I need the 4T as space to write stuff in.
in the context of the upcoming question:
- Let us abstract the arc and slog [or is it called zil] that are in ram for a moment.
- Let us also abstract the no redudancy, no failsafe in case nvme drive fails.
- from now on when I say cache, I mean the cache that is physicaly on the nvme ssd.
If I use one nvme I use 4x pcie lanes, one nand controler, one hardware cache
If i use 2 nvme in the same pool, i use 8x lanes (4 on each controler), 2 controlers, two different hardware cache
this next paragraph is the question, stated in many different ways
How does ZFS decide to write to the underlying nvme ssd if they are both in the pool?
does zfs fill up one drive, then the second
does zfs blindly writes odd bits on nvme0 and even bits on nvme1
does zfs balances the load as much as it can between the two drives/controllers
bonus question can i expect speed increase in the two nvme configuration? ( I am effectively doubling the lanes and cache afterall )
thank you for reading, have a nice day
EDIT: i have google in search of the following information:
what is the size of the cache on the corsair MP600 4to
I could not find it (i do not know if the cache is bigger on the 4to, compared to the 2to). This means i do not know if going for 2 ssd would double the cache size, but i know for a fact it would spread the load over 8 lanes instead of 4 and two controlers instead of one.
4to and 2To have the same physical config, it’s onlythe dynamic cache that differs.
i’m going for two drives, so that te workload is divided into two NVMe thus increasing speed. (as stated below, that increase is counterbalanced by the fact the arc is counter productive when it comes to nvme ; but the overhaul is stil an increase)