disk preallocation setting, what is posix_fallocate?

[Red Squirrel]

i want to setup my stores to preallocate disks, that way they will not grow out of range like with thin provision. I have 40GB disks in vmware that are well over 2TB as they have just grown over time. So I want to avoid that.

There is an option for "Full" and also an option for "Full (posix_fallocate)". What is the 2nd one and which one should I be using? I don't want to use sparse files as those are weird and confusing to deal with I just want normal files that take up the space immediately and stay that size unless I grow it manually.

 

[_gabriel]

i want to setup my stores to preallocate disks

afaik, you loose trim doing that, so with SSD, I should only thin allocation.

 

[Red Squirrel]

I'm using all HDDs for mass storage, mostly raid 10. Raid 5 for stuff that's less performance critical.

Although is there a way to cap the thin allocation so it never grows beyond the set size? I'd be fine with that too.

 

[_gabriel]

it never grows beyond the set size

iirc, only snapshots grow beyond the set size. they should be only temporary.
Without snapshots set size cannot be exceeded, and of course don't over allocate space.

 

[Red Squirrel]

Oh ok that's good to know, with vmware I found a vmdk that is over 3TB even though the drive is only 40GB in reality. But maybe Proxmox is better to avoid that from happening. So I will just leave the setting alone then.