some ZFS questions

Andrew Berg aberg010 at
Wed Aug 6 08:49:52 UTC 2014

On 2014.08.06 02:32, Scott Bennett wrote:
>      I have a number of questions that I need answered before I go about
> setting up any raidz pools.  They are in no particular order.
> 	1) What is the recommended method of using geli encryption with
> 	ZFS?

> Does one first create .eli devices and then specify those
> 	.eli devices in the zpool(8) command as the devices to include
> 	in the pool? 

> 	2) How does one start or stop a pool?
That depends on what you mean by 'start' and 'stop'. I am guessing by what you
described that you mean 'import' and 'export'. I'm not sure how to prevent
automatic import for pools that were imported on the same system and not
exported prior to shutdown, but I am sure it can be done. Resilvering does not
mercilessly thrash disks; standard reads and writes are given higher priority
in the scheduler than resilver and scrub operations.

> 	3) If a raidz2 or raidz3 loses more than one component, does one
> 	simply replace and rebuild all of them at once?  Or is it necessary
> 	to rebuild them serially?  In some particular order?
AFAIK, replacement of several disks can't be done in a single command, but I
don't think you need to wait for a resilver to finish on one before you can
replace another.

> 	5) When I upgrade to amd64, the usage would continue to be low-
> 	intensity as defined above.  Will the 4 GB be enough?  I will not
> 	be using the "deduplication" feature at all.
It will be enough unless you are managing tens of TB of data. I recommend
setting an ARC limit of 3GB or so. There is a patch that makes the ARC handle
memory pressure more gracefully, but it's not committed yet. I highly recommend
moving to 64-bit as soon as possible.

> 	6) I have a much fancier computer sitting unused that I intend to
> 	put into service fairly soon after getting my current disk and data
> 	situation resolved.  The drives that would be in use for raidz
> 	pools I would like to attach to that system when it is ready.  It
> 	also has 4 GB of memory, but would start out as an amd64 system and
> 	might well have another 2 GB or 4 GB added at some point(s), though
> 	not immediately.  What problems/pitfalls/precautions would I need
> 	to have in mind and be prepared for in order to move those drives
> 	from the current system to that newer one?
It should be pretty painless to move pools from system to system. Exporting a
pool from the old system is recommended before moving, but not necessary.

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