ZFS l2arc and HAST ? newbie question

[Thomas Steen Rasmussen]

Hello list,

I am playing with HAST in order to build some redundant storage
for a mailserver, using ZFS as the filesystem.
I have the following zpool layout before stating the HAST experiments:

         NAME              STATE     READ WRITE CKSUM
         tank              ONLINE       0     0     0
           raidz2          ONLINE       0     0     0
             label/hd4     ONLINE       0     0     0
             label/hd5     ONLINE       0     0     0
             label/hd6     ONLINE       0     0     0
             label/hd7     ONLINE       0     0     0
         logs              ONLINE       0     0     0
           mirror          ONLINE       0     0     0
             label/ssd0s1  ONLINE       0     0     0
             label/ssd1s1  ONLINE       0     0     0
         cache
           label/ssd0s2    ONLINE       0     0     0
           label/ssd1s2    ONLINE       0     0     0

As I understand it, to accomplish this with HAST I will need to make a
HAST resource for each physical disk, like so:

         NAME              STATE     READ WRITE CKSUM
         tank              ONLINE       0     0     0
           raidz2          ONLINE       0     0     0
             hast/hahd4    ONLINE       0     0     0
             hast/hahd5    ONLINE       0     0     0
             hast/hahd6    ONLINE       0     0     0
             hast/hahd7    ONLINE       0     0     0

But what about slog and cache devices, currently on SSD disks for
performance reasons ? It doesn't really make sense to synchronize
a cache disk over the network, does it ?

Could I build the zpool with the SSD disks directly (without
HAST) and would ZFS survive an export/import on the other host,
when the cache disks are suddently different ? I am thinking cache
only here, not slog.

Do SSD l2arc / slog even make any sense when I am "deliberately"
slowing down the filsystem with network redundancy anyway ?

Oh, and is there any problems using labels for HAST devices ? My
controller likes to give new device names to disks now and then,
and it has been a blessing to use labels instead of device names,
so I'd like to continue doing that when using HAST.

If needed, any testing on my part will unfortunately have to wait a
couple of days for the MFC of the HAST fix from yesterday, as the SEQ
issue is preventing me from further experiments with HAST for now.

Thank you for any input, and _THANK YOU_ for the work on both ZFS
and HAST, their combined awesomeness is reaching epic proportions.

Best regards

Thomas Steen Rasmussen