From: Brendan Hide <brendan@swiftspirit.co.za>
To: Martin <m_btrfs@ml1.co.uk>, linux-btrfs@vger.kernel.org
Subject: Re: What to do about snapshot-aware defrag
Date: Sun, 01 Jun 2014 01:51:49 +0200 [thread overview]
Message-ID: <538A6B15.3080609@swiftspirit.co.za> (raw)
In-Reply-To: <lmav1p$ih7$1@ger.gmane.org>
On 2014/05/31 12:00 AM, Martin wrote:
> OK... I'll jump in...
>
> On 30/05/14 21:43, Josef Bacik wrote:
>> [snip]
>> Option 1: Only relink inodes that haven't changed since the snapshot was
>> taken.
>>
>> Pros:
>> -Faster
>> -Simpler
>> -Less duplicated code, uses existing functions for tricky operations so
>> less likely to introduce weird bugs.
>>
>> Cons:
>> -Could possibly lost some of the snapshot-awareness of the defrag. If
>> you just touch a file we would not do the relinking and you'd end up
>> with twice the space usage.
> [...]
>
>
> Obvious way to go for fast KISS.
I second this - KISS is better.
Would in-band dedupe resolve the issue with losing the
"snapshot-awareness of the defrag"? I figure that if someone absolutely
wants everything deduped efficiently they'd put in the necessary
resources (memory/dedicated SSD/etc) to have in-band dedupe work well.
> One question:
>
> Will option one mean that we always need to mount with noatime or
> read-only to allow snapshot defragging to do anything?
That is a very good question. I very rarely have mounts without noatime
- and usually only because I hadn't thought of it.
> Regards,
> Martin
--
__________
Brendan Hide
http://swiftspirit.co.za/
http://www.webafrica.co.za/?AFF1E97
next prev parent reply other threads:[~2014-05-31 23:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-30 20:43 What to do about snapshot-aware defrag Josef Bacik
2014-05-30 22:00 ` Martin
2014-05-31 23:51 ` Brendan Hide [this message]
2014-06-01 1:52 ` Duncan
2014-06-02 3:07 ` Mitch Harder
2014-06-02 13:19 ` Josef Bacik
2014-06-02 13:22 ` Josef Bacik
2014-06-03 23:54 ` Martin
2014-06-04 9:19 ` Erkki Seppala
2014-06-04 13:15 ` Martin
2014-06-04 19:33 ` Chris Murphy
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