System Dataset Pool Size? Setup on Dedicated Volume

[TXAG26]

By default, FreeNAS installed the "System Dataset Pool" on my Raidz2 volume. I would like to create two vmdisks and mirror them together and move the "System Dataset Pool" to this new volume. I've done a quick search through the FreeNAS guide and have been unable to determine what size a dedicated volume for the "System Dataset Pool" needs to be.

The FreeNAS manual makes reference that this pool might be used for future FreeNAS development/features, so I'd like to set it large enough, but not too large as I'd like to thin-provision this on an SSD since it is accessed constantly for logging purposes.

Any ideas on what size to make this volume?

 

[cyberjock]

vmdisks!? Are you running FreeNAS in a VM or something!?

 

[TXAG26]

vmdisks!? Are you running FreeNAS in a VM or something!?

Of course I am! I have been for awhile now, it is set up properly with PCI-passthrough for the HBA and according to all of the best practices (no corners cut) and I frequently perform external backups.
Anyways, back to my original question - how much total disk space does the "System Dataset Pool" need?

 

[TXAG26]

Any ideas? This isn't an ESXI-specific question as one may want to move the System Dataset Pool to another physical volume in there system.

 

[enemy85]

I guess you will be ok with 128gb disks (probably much even less would be ok, but who knows...)

 

[mjws00]

Just check to see how big it is and add some multiplier that makes you comfortable. 'du -hs .system'
On my ~1yr old install it is 8MB and the bulk is cores. So I would think anything over a GB or two is overkill. But my log doesn't spew.

You can also resize a vmdk at will. So start small and bump it if you feel like it.

I'd also prefer real information on the implications of .system failure vs. hyperbole. Only a few versions ago we were logging to RAM drive. From what I can see it is only Samba that needs persistent storage. I've certainly never had FreeNAS puke or even blink when nuking the pool with .system. It also boots and runs fine with no pool at all. I could see it making a mess with Active Directory, but that may have been patched or addressed, as frankly a Samba system taking out an AD forest because it is missing a file is unacceptable.

Obviously having it live on a huge redundant pool is safest. But there is also something to be said for separation of 'system/logging' and data. Samba kind of forced a compromise imho. This is a workaround for the flexibility of USB boot devices. If the os lives on an ssd or even a sata DOM the compromise is unnecessary. TrueNAS throws swap on the DOM, I didn't check to see where it puts .system but I doubt they stuff it on a random pool.

Two bits. You're already off the straight and narrow. Give it a little pool and continue to enjoy.

 

[TXAG26]

I created 2 vmdisks (8GB ea.) on my main ESXI SSD and set up a mirrored ZFS volume in FreeNAS, which ended up at about 6GB usable. Using the FreeNAS web gui, I changed the system dataset from my primary data volume to the vmdisk and it took about 30 seconds to complete, so I'm guessing the size of files transferred and living there are not too large.

Everything seems to be working so far. (Hopefully these aren't famous last words).

It's my understanding that this is currently only used by Samba and for logging, so if it runs out of space, it should not crash FreeNAS or corrupt data, correct? At worst, I may have to re-create a couple file shares, right?

 

[TXAG26]

After 24hrs, the System Dataset Pool is only using 17MB and has an 8.1x compression ratio (lz4) with 5.8GB free space. This should be more than enough space. I also turned on logging so that the performance logs do not disappear during every update/reboot.