On 2014/05/20 04:07 PM, Austin S Hemmelgarn wrote:
On 2014-05-19 22:07, Russell Coker wrote:
[snip]
As an aside, I'd really like to be able to set RAID levels by subtree. I'd
like to use RAID-1 with ditto blocks for my important data and RAID-0 for
unimportant data.
But the proposed changes for n-way replication would already handle
this.
[snip]
Russell's specific request above is probably best handled by being able
to change replication levels per subvolume - this won't be handled by
N-way replication.
Extra replication on leaf nodes will make relatively little difference
in the scenarios laid out in this thread - but on "trunk" nodes (folders
or subvolumes closer to the filesystem root) it makes a significant
difference. "Plain" N-way replication doesn't flexibly treat these two
nodes differently.
As an example, Russell might have a server with two disks - yet he wants
6 copies of all metadata for subvolumes and their immediate subfolders.
At three folders deep he "only" wants to have 4 copies. At six folders
deep, only 2. Ditto blocks add an attractive safety net without
unnecessarily doubling or tripling the size of *all* metadata.
It is a good idea. The next question to me is whether or not it is
something that can be implemented elegantly and whether or not a
talented *dev* thinks it is a good idea.
--
__________
Brendan Hide
http://swiftspirit.co.za/
http://www.webafrica.co.za/?AFF1E97
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