[zfs-discuss] Advice about ashift, grub, dedup etc. 3 questions.

Swâmi Petaramesh swami at petaramesh.org
Fri Jan 31 10:31:41 EST 2014

Hi again,

Waiting to receive 2 new HDs, I'm not yet sure whether they will be 4KB or 
512B sectors sized, assuming 4k, but anyway...

When creating a new pool onto them, would I be wise to use "ashift=9" so it 
will use 4k blocks and it leaves the path open for the future ?

Or did I miss something ?

In a previous post I also said that grub stopped allowing me to boot from my 
zpool. Thinking twice about it, it seemed this happened when I upgraded my 
previous zpool to "version 5000" and allowed LZ4 compression. Looks like grub 
didn't recognize my zpool format/features anymore thereafter.

So the other question is : Is it better to leave my /boot outside of ZFS, so I 
will always be independant from "what ZFS features does grub support or not", 
or would it be wiser to create a pool with an older version - if yes, which 
one and what would be the drawback ?

Last, my current (damaged) pool uses deduplication, and I could see that the 
performance and memory impact was huge, so I'd rather start again without 
dedup at all (I'm getting bigger disks).

Given that I will "zfs send foo | zfs receive bar" from the old pool to the 
new one, is there a way that I can make sure that I will have dedup off on the 
new pool, even though the data is actually dedup'd on the old pool. Is there a 
way I could just completely turn the dedup feature off for the whole new pool? 


Kind regards.

Swâmi Petaramesh <swami at petaramesh.org> http://petaramesh.org PGP 9076E32E

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