How to remove the OpenSolaris ZFS dump device

Question

The ZFS dump device is used only for debugging problems. In this case, I have decided the risk vs reward is such that I should delete the dump device to make room for other storage.

I am able to disable save-core (copy from dump device to /var/crash) using dumpadm -n, but when I run zfs destroy rpool/dump, I still get
cannot destroy 'rpool/dump': dataset is busy, indicating that dumpadm -n was insufficient.

How can I disable and remove this dedicated dump device?

Solution

Specify another location for dumpadm to use crash dumps instead of just disabling them.

dumpadm -d swap

Source: http://comments.gmane.org/gmane.os.solaris.opensolaris.zfs/19529

Comments

[700 Software]

This won't work for me because I removed the swap device to save disk space. There was so much free RAM that swap could not have improved performance.

[notpeter]

I haven't tried this myself, but if you read the link it suggest that even you don't have a suitable swap device, telling it to use swap will set it to 'none' so it's no longer using your dump device. Can't hurt to try.

[700 Software]

I already tried. It didn't work.

[notpeter]

Since you're just trying to reclaim the space, can you resize the dump volume to something silly small like zfs set volsize=1M rpool/dump?

[700 Software]

Yep. That silly solution seems to be the best I can do.

[700 Software]

I might give it a try next time I'm working on a staging server, but at first glance it looks like the linked page is solving dataset already exists, while my question is about dataset is busy. So maybe it will work and maybe it won't...

[700 Software]

This looks like a very helpful command. I have an idea on how zdb could make my reporting scripts more accurate.

[700 Software]

Doesn't seem to work. No results output from the command.

[700 Software]

If 1M doesn't work (out of space), try a larger value like 8M, which worked for me on OmniOS/Illumos.