System Dataset Growth by 15GB in 1 day

[Gulftown]

I have a single 16GB SLC SSD as volume 0. The only thing i think i am storing there is the system dataset. This has worked fine for about a year and then about a week ago a problem developed. The freespace on this volume went from nearly 100% to 0%. If it matters i can post an image of the volume free space but it shows a gradual drop of freespace over a 24 hour period.

1) How do i find out if anything but the system dataset is being written to this Volume? There are no datasets defined on the volume
2) if it is in fact the system dataset that grew to 15.xGB over that period...how do i clean the system dataset?

The only other thing i can think is that the drive for some reason went belly up and the lack of free space is due to drive capacity dropping (memory somehow assigned as bad) vs. amount of data growing.

Any suggestions as to what i am overlooking or how to appropriately troubleshoot?

 

[SweetAndLow]

If there are no datasets how is the system dataset on it? You should supply more information on your setup. Do you have half on it? I'd it mirrored or part of a pool?

 

[Gulftown]

Volume 0: single 16GB SLC SDD
Volume 1: 4 drives, RAIDz2. 2 datasets
FreeNAS-9.3-STABLE-201505130355

Volume 0 does not have a dataset defined, but when under system --> dataset, i chose Volume 0 for my system dataset pool. I assumed it just took over free space on the volume for the system dataset. Don't know what other config info is relevant.

Looking at attached chart - i don't see growth in used space...but i don't know how to check the SSD health to see if in fact blocks are being marked as bad

Edit: turns out i confused myself with bad nomenclature. I actually created a dataset called volume 0 on Volume0 (no idea what i was thinking). Long story short, i moved the system dataset from Volume0 to volume 1 (system --> system dataset), then "destroyed dataset" volume 0. which allowed me to reclaim all the space (see attached file volume 0 clean). I am now going to move the system dataset back.

I think the problem is resolved...but it concerns me i never actually found out what the problem was or what caused the problem.

 

[danb35]

I actually created a dataset called volume 0 on Volume0 (no idea what i was thinking).

No you didn't; ZFS automatically does that any time you create a pool. Every pool contains a dataset of the same name as the pool; any datasets you create will be children of that dataset. That dataset was hidden prior to FreeNAS 9.3.

 

[SweetAndLow]

Any smart errors from the drive?

 

[Gulftown]

no errors on any other drives in the system. I had a mistake in my SMART test setup so that drive ada4, was not running regular tests. I just ran one now and it reported ok

Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error
# 1 Reserved (0x80) Completed without error 00% 8528 -