From: Martin <m_btrfs@ml1.co.uk>
To: linux-btrfs@vger.kernel.org
Subject: Re: ditto blocks on ZFS
Date: Sat, 17 May 2014 13:50:52 +0100 [thread overview]
Message-ID: <ll7lvd$ulk$1@ger.gmane.org> (raw)
In-Reply-To: <2308735.51F3c4eZQ7@xev>
On 16/05/14 04:07, Russell Coker wrote:
> https://blogs.oracle.com/bill/entry/ditto_blocks_the_amazing_tape
>
> Probably most of you already know about this, but for those of you who haven't
> the above describes ZFS "ditto blocks" which is a good feature we need on
> BTRFS. The briefest summary is that on top of the RAID redundancy there...
[... are additional copies of metadata ...]
Is that idea not already implemented in effect in btrfs with the way
that the superblocks are replicated multiple times, ever more times, for
ever more huge storage devices?
The one exception is for SSDs whereby there is the excuse that you
cannot know whether your data is usefully replicated across different
erase blocks on a single device, and SSDs are not 'that big' anyhow.
So... Your idea of replicating metadata multiple times in proportion to
assumed 'importance' or 'extent of impact if lost' is an interesting
approach. However, is that appropriate and useful considering the real
world failure mechanisms that are to be guarded against?
Do you see or measure any real advantage?
Regards,
Martin
next prev parent reply other threads:[~2014-05-17 12:51 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 [this message]
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
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
-- strict thread matches above, loose matches on Subject: below --
2014-05-22 15:28 Tomasz Chmielewski
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