2012-10-14 2:41, Michael Armstrong wrote:
Ok, so it is possible to remove. Good to know, thanks . I move the pool maybe 
once a month for a few days, on an otherwise daily used fixed location. So 
thought the warm up allowance may be worth it. I guess I just wanted to know if 
adding a cache device was a one way operation or not and whether or not it 
risked integrity.

I haven't *tried* your scenario, but I *believe* that:

1) Loss of L2ARC should not be fatal to a pool - reads should just
fall back to main pool, so even an occasional export without removal
should work;

2) Removal and addition of L2ARC on the fly does work - tested that ;)

3) As of now, upon pool import (and/or L2ARC attachment) the cache
device is considered empty. So any such porting of the disk, as well
as reboots of the computer, will cause new cache warm-up (and some
SSD wear).

4) If your portable disk is USB and practically limited by the bus
and protocol, you may have benefits from caching of its hot data
in RAM and SSD (ARC and L2ARC) - if the data from this pool is used
heavily enough.

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