Problem trying to create VM

[shuhdonk]

I am new to proxmox and relatively new to linux. I have a new server i just built and installed proxmox for the first time. I am trying to create a windows vm with 8tb of space but getting an out of disk space error. I am using 4 4tb ssds in raidz1 configuration. Here is my zfs screen and can see error message at bottom when trying to create the vm. idea?

 

[shuhdonk]

Okay, so it will let me create a 7TB window vm but not anything larger. I have over 10 tb of available space on my drive.. any reason for this and a way to "fix" it?

So it allowed me to create a 7tb windows vm (3 4tb sdds in raidz option in proxmox, which should be ~10.5gb available space). After creating the windows 7tb vm I tried creating a ubuntu vm with 256gb space and same msg, out of space.. it allowed me to create a 32gb one though. Is raidz option eating up that much space? I thought raidz was a raid 5 array.. which should give me that ~10.5tb of usable space.

As of now it is only allowing me to use barely over 7tb of space.

 

[bobmc]

I don't know if this is the answer but I think this may be a windows related limitation regarding the number of disk sectors supported. Disk manufacturers 'lie' to windows about the number of real sectors on disk to work around this restriction and it's possible that's what is tripping up the system here - the virtual disk cannot perform the same trick regarding sector size.

Not certain as I say but that would be my suspicion

 

[aaron]

Checkout the following chapter in the docs regarding ZFS pool design considerations for a VM workload: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_raid_considerations

TL;DR: with zvols you have a fixed size for parity data on any raidz and therefore the data to parity ratio can be quite bad. Filesystem datasets don't suffer from it that badly because they use a variable recordsize.

For a VM workload you get the best performance with a raid10 like pool made of mirror vdevs and avoid parity problems.

Also be aware that you should not fill up a ZFS pool more than 80% because performance will suffer once it gets too full.