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Re: [RFC/PATCH] svnadmin: recover/hotcopy erroring out for old FSFS repositories

From: Ivan Zhakov <ivan_at_visualsvn.com>
Date: Fri, 31 Jan 2014 14:58:45 +0400

On 31 January 2014 14:57, Ivan Zhakov <ivan_at_visualsvn.com> wrote:
> On 31 January 2014 05:50, Evgeny Kotkov <evgeny.kotkov_at_visualsvn.com> wrote:
>>> This only affects non-sharded repositories with rev-local IDs,
>>> i.e. those in SVN 1.4 format. For those, it is writing 3 files
>>> instead of 2 per rev now.
>>
>> I assume you are talking about r1560723 [1]. If I read the code correctly...
>> [[[
>> if ( (!max_files_per_dir || rev % max_files_per_dir == 0)
>> && dst_ffd->format >= SVN_FS_FS__MIN_NO_GLOBAL_IDS_FORMAT)
>> SVN_ERR(hotcopy_update_current(&dst_youngest, dst_fs, rev, iterpool));
>> ]]]
>>
>> ...hotcopy now checkpoints after every revision for all non-sharded repositories
>> with FSFS format >= 3. So, checkpointing happens for all FSFS format 1/2
>> repositories upgraded via 'svnadmin upgrade' (with linear layout), that were
>> not fsfs-reshard'ed or dump/loaded into a repository with newer format.
>>
>> I am not aware of how many people reshard or dump/load their old repositories
>> after upgrade, but I did a quick benchmark for a real-world repository and on my
>> machine it shows 7x performance degradation with checkpointing enabled. Is it
>> worth the ability to re-run the backup from a checkpoint upon cancellation?
>>
>> [[[
>> # svnrdump http://googletest.googlecode.com/svn/trunk/
>> # load the dump into a --compatible-version=1.3 repository
>> # upgrade the repository with the most recent svnadmin
>>
>> # disable checkpointing, benchmark making 100 hotcopy backups:
>> real 0m18.741s
>> user 0m2.552s
>> sys 0m13.432s
>>
>> # now enable checkpointing and repeat the benchmark:
>> real 2m5.793s
>> user 0m0.836s
>> sys 0m34.840s
>> ]]]
>>
>> [1] http://svn.apache.org/viewvc?view=revision&revision=r1560723
>>
> That's what I suspected. In this case I think r1560723 should not be
> backported to 1.8.x for the following reasons:
> 1. Significant performance degradation for 'svnadmin hotcopy' with
> '--incremental' flag.
I meant "without '--incremental' flag"

-- 
Ivan Zhakov
CTO | VisualSVN | http://www.visualsvn.com
Received on 2014-01-31 11:59:39 CET

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