ZFS pool - entire device or partition

[kappclark]

I am dipping my toes into the ZFS pool, so to speak, an was wondering if it makes any difference if you setup a mirrored pool with partitions vs entire devices...

I went ahead and partitioned 2 1 TB HD's with 1 partition each... I then did zpool create -f -o ashift=12 vmpool mirror /dev/sdb1 /dev/sdc1 - no errors ....

Is there any reason not to do it this way ??

THX

 

[Republicus]

I don't think there is any problem in using partitions. Make sure they are GPT and I would suggest using /dev/disk/by-id intead of /dev/sdXx

 

[kappclark]

Good idea about disk-by-id ... the /dev/sdxx id can change when other hw is attached -- seems like a time bomb, set to go off when connect an external USB hd --

 

[LnxBil]

Is there any reason not to do it this way ??

Yes, first and most importantly: ZFS will also create a partitions for you if you use the whole device. So you will save time in not creating them manually. The idea is to have a partition at the end that is a very small (a few MB, depending on the size of your disk) in order to combine disks from the different vendors. Not all of them have the same disk size even if they claim to be e.g. 1 TB in size.

 

[kappclark]

THX - I setup a mirror this AM with just the devices - how easy.. did not use disk-by-id ... added the pool to Proxmox, and setup some storage containers in the pool for ISO, VM, containers, templates etc...

One concern - I see an unexpected amount of memory use - for example - the host I just re-built (an old ESXi box) had 16GB DDR3.. I have 3 Windows VM's running ...the total memory they are allocated is 2 + 2 +1 = 5GB total.

Yet when I look at the summary page for the host, I see 13.6 GB used ... I went ahead and shut down the VMs (and 1 Alpine container) - and it says 8.7 GB in use !

is this the price one pays for ZFS ? guess I will need to add more memory if I plan to deploy more VMs ....

 

[LnxBil]

is this the price one pays for ZFS ? guess I will need to add more memory if I plan to deploy more VMs ....

Yes. Der default, ZFS uses half your memory as adaptive replacement cache (ARC). You can limit the amount of memory used for caching by reading this. The article is in general a good entry point into the work of ZFS.

 

[kappclark]

Thanks -

I see no zfs.conf in that directory ( /etc/modprobe.d/) ... could it be in another directory ? maybe hidden ?

Maybe I need to create it ?

 

[LnxBil]

Maybe I need to create it ?

Yes