Re: [zfs-discuss] backwards/forward compatibility

2010-04-28 Thread Ian Collins

On 04/29/10 10:21 AM, devsk wrote:

I had a pool which I created using zfs-fuse, which is using March code base 
(exact version, I don't know; if someone can tell me the command to find the 
zpool format version, I would be grateful).

   

Try [zfs|zpool] upgrade.

These commands will tell you the current supported version and the 
version of each pool/filesystem.  If the command makes you nervous, run 
it as a normal user!



I exported it and now I tried to import it in OpenSolaris, which is running Feb 
bits because it says 134 Feb 2010 in uname output (2009-06 updated with pkg 
image-update). It fails to import it because of incompatible version.

   

b134 will be using pool version = 22.


Backward compatibility is a given and I know Solaris will never compromise on 
that and Sun has been industry leader in that. What about forward 
compatibility? I would think zfs pool format would be stable by now.

   
No, newer pool support newer features.  Imagine the arse ache you would 
experience importing a dedup poll to a system then didn't support it!

So, what happened here? I know I am going to get shouted at for saying this but 
this tells me that ZFS is still not on-disk stable in the same vein as BTRFS is 
not on-disk stable. But it gets better. I can mount and use BTRFS FSs which 
were created after 2.6.32 (which was a long ago) in a 2.6.32 kernel i.e. I can 
boot my older kernel if I need to and still access the newer FS and files in 
it, without breaking anything. Of course, the newer kernels work with FSs 
created in older kernels.

   
You can create pools and filesystems with older versions if you want 
them to be backwards compatible.  I have done this when I was sending 
data to a backup server running an older Solaris version.

May be I am doing something wrong. May be it is just about using '-f' flag and 
things will work out and nothing will break. Is it? I look fwd to guidance from 
the community on this.
   


Post back the output of the upgrade commands an the errors you get when 
importing the pool.


--
Ian.

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Re: [zfs-discuss] backwards/forward compatibility

2010-04-28 Thread Bob Friesenhahn

On Thu, 29 Apr 2010, Ian Collins wrote:
You can create pools and filesystems with older versions if you want them to 
be backwards compatible.  I have done this when I was sending data to a 
backup server running an older Solaris version.


From the zpool manual page, it seems that it should be possible to 
create an older pool version using newer software.  Of course, it is 
also necessary to make sure that any created filesystems are a 
sufficiently low version.


Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,http://www.GraphicsMagick.org/
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