zfs discuss - May 2010 - Can I recover filesystem from an offline pool?

Hi All, is there any procedure to recover a filesystem from an office pool or
bring a pool on-line quickly.
Here is my issue.
* One 700GB Zpool 
* 1 filesystem with compression turn on (only using few MB)
* Try to migrated another filesystem from a different pool with dedup stream.
with
zfs send -D | zfs receive 
* The system hung.
* reboot the system, the system would hang trying to recover or remove the
snapshot on the 700GB zpool.  The HD light would flash for hours on then go
quiet  and the whole system hang.
* reboot the system without the 700GB zpool disk detached. system boot up just
fine.  attach the disk and run zfs clear (-F) <pool name> then The HD
light would flash for hours on then quiet and the whole system hang.

I am not interested in the filesystem is having problems.  I would like the to
copy the data out of first filesystem that are only a few MB.

Anyway I can copy the data out or remove the problem filesystem with the zpool
offline or bring the pool on-line without the recover/remove process to the
problem filesystem.
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This message posted from opensolaris.org

10GB of memory + 5 days later.  The pool was imported.
this file server is a virtual machine.  I allocated 2GB of memory and 2 CPU
cores assume this was enough to mange 6 TB (6x 1TB disks). While the pool I am
try to recover is only 700 GB and not the 6TB pool I am try to migrate.

So I decided to borrow all available memory for this vm and increase it to 12
GB.  What I immediately notice is the system does not hang as before and Hard
drive activity light continue to flash so I left it running.

After Days later the pool as imported.
Here is some of my stats
1. system is running opensolaris svn_134
2. The pool I try to recover/import show about 150GB data with 50GB allocation
3x dedupped before the zfs send hung.
3.  The Memory usage during the import showing around 2GB of free space i.e.
10GB used
4. The zpool would walk up once in a while for only a sec or so. very low CPU
usage.  I remember seeing only 2min of CPU time after 2 days.
5. during this whole import, all other zfs commands are blocked, also include
not able to open new shell and SSH would hang after password is entered.

I assume this issue is all due to the new dedup feature any only happen to pool
containing dedupped dataset.  Hopeful this issue fixed and available for testing
soon.

I thought the memory available for ARC cache are for performance only.   I am
surprise to learn having not enough available memory would actually hang system
when you are deleting a dedupped dataset .  I would consider this a major issue
as the memory requirement seem to be depend on the characteristic of the
dedupped dataset and there doesn''t seem to have a good document
explaining how much memories are needed.

Hope this help will anyone consider testing the dedup feature
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