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zfs: 9 vs current, and ZIL/L2ARC on ssd?



I am about to try to use zfs for the first time and have a few
questions.

I have a machine that is running NetBSD-9/amd64 with 2 cores, 8G of RAM,
a single 1T SSD, with a smallish root/swap/usr, and about 870 GiB free
intended for zfs.  I am heading for one po0l that is not raid at all.

I'm not all that worried about transitions or stability; this is a build
machine for packages, not particularly precious, and it being down for a
week while I fix it is no big deal.

I will likely pivot the machine to be xen dom0; I hope that doesn't
matter much (other than 1 core only in the dom0).  Or I might use nvmm,
or both.

I might add a spinning disk later, either internal or USB.  (I realize
that there, I probably want both ZIL and L2ARC on SSD.  I would rather
move bits later than do things now to ease that, since I do not have an
actual plan.)

My questions are:

  Is 9/current close enough to the same zfs code that it doesn't matter
  which I run?  If I'm inclined to run current for other reasons, is
  that a bad idea zfs-wise?

  I understand that zfs has an intent log always, and that can be within
  the pool, or one can add a ZIL device.  With the pool having one
  device which is an SSD, I see no point in partitioning off part of
  that SSD to be the ZIL.

  I understand that zfs has ARC in RAM, and can have L2ARC on disk.
  Given that the pool is on SSD, it seems pointless to split off some
  for L2ARC.

My expected answers are:

  The code is basically the same and it doesn't really matter but
  probably current has some bugfixes 9 doesn't.  There's no reason
  current is scary becuase of zfs.

  There is no point in a ZIL on the same SSD as the pool.

  There is really no point in L2ARC on the same SSD as the pool.


Corrections/clues appreciated.

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