From: Brendan Hide <brendan@swiftspirit.co.za>
To: Austin S Hemmelgarn <ahferroin7@gmail.com>,
russell@coker.com.au, linux-btrfs@vger.kernel.org
Subject: Re: ditto blocks on ZFS
Date: Tue, 20 May 2014 22:11:16 +0200 [thread overview]
Message-ID: <537BB6E4.2020508@swiftspirit.co.za> (raw)
In-Reply-To: <537B6190.2030100@gmail.com>
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
next prev parent reply other threads:[~2014-05-20 20:11 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-16 3:07 ditto blocks on ZFS Russell Coker
2014-05-17 12:50 ` Martin
2014-05-17 14:24 ` Hugo Mills
2014-05-18 16:09 ` Russell Coker
2014-05-19 20:36 ` Martin
2014-05-19 21:47 ` Brendan Hide
2014-05-20 2:07 ` Russell Coker
2014-05-20 14:07 ` Austin S Hemmelgarn
2014-05-20 20:11 ` Brendan Hide [this message]
2014-05-20 14:56 ` ashford
2014-05-21 2:51 ` Russell Coker
2014-05-21 23:05 ` Martin
2014-05-22 11:10 ` Austin S Hemmelgarn
2014-05-22 22:09 ` ashford
2014-05-23 3:54 ` Russell Coker
2014-05-23 8:03 ` Duncan
2014-05-21 23:29 ` Konstantinos Skarlatos
2014-05-22 15:28 Tomasz Chmielewski
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