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From: Goffredo Baroncelli <kreijack@libero.it>
To: Christoph Anton Mitterer <calestyo@scientia.net>,
	Nikolay Borisov <nborisov@suse.com>,
	Alex Adriaanse <alex@oseberg.io>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: Ongoing Btrfs stability issues
Date: Sun, 11 Mar 2018 18:51:19 +0100	[thread overview]
Message-ID: <01ddb562-f1e2-25cf-0a8a-ffaa43b867d3@libero.it> (raw)
In-Reply-To: <1520692153.24363.15.camel@scientia.net>

On 03/10/2018 03:29 PM, Christoph Anton Mitterer wrote:
> On Sat, 2018-03-10 at 14:04 +0200, Nikolay Borisov wrote:
>> So for OLTP workloads you definitely want nodatacow enabled, bear in
>> mind this also disables crc checksumming, but your db engine should
>> already have such functionality implemented in it.
> 
> Unlike repeated claims made here on the list and other places... I
> woudln't now *any* DB system which actually does this per default and
> or in a way that would be comparable to filesystem lvl checksumming.
> 

I agree with you, also nobody warn that without checksum in case of RAID filesystem BTRFS is not capable anymore to check if a stripe is correct or not

> 
> Look back in the archives... when I've asked several times for
> checksumming support *with* nodatacow, I evaluated the existing status
> for the big ones (postgres,mysql,sqlite,bdb)... and all of them had
> this either not enabled per default, not at all, or requiring special
> support for the program using the DB.
> 
> 
> Similar btw: no single VM image type I've evaluated back then had any
> form of checksumming integrated.
> 
> 
> Still, one of the major deficiencies (not in comparison to other fs,
> but in comparison to how it should be) of btrfs unfortunately :-(

COW is needed to properly checksum the data. Otherwise is not possible to ensure the coherency between data and checksum (however I have to point out that BTRFS fails even in this case [*]).
We could rearrange this sentence, saying that: if you want checksum, you need COW...

> 
> 
> Cheers,
> Chris.
> --
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> 

[*] https://www.spinics.net/lists/linux-btrfs/msg69185.html

-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

  reply	other threads:[~2018-03-11 17:51 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-15 16:18 Ongoing Btrfs stability issues Alex Adriaanse
2018-02-15 18:00 ` Nikolay Borisov
2018-02-15 19:41   ` Alex Adriaanse
2018-02-15 20:42     ` Nikolay Borisov
2018-02-16  4:54       ` Alex Adriaanse
2018-02-16  7:40         ` Nikolay Borisov
2018-02-16 19:44 ` Austin S. Hemmelgarn
2018-02-17  3:03   ` Duncan
2018-02-17  4:34     ` Shehbaz Jaffer
2018-02-17 15:18       ` Hans van Kranenburg
2018-02-17 16:42         ` Shehbaz Jaffer
2018-03-01 19:04   ` Alex Adriaanse
2018-03-01 19:40     ` Nikolay Borisov
2018-03-02 17:29       ` Liu Bo
2018-03-08 17:40         ` Alex Adriaanse
2018-03-09  9:54           ` Nikolay Borisov
2018-03-09 19:05             ` Alex Adriaanse
2018-03-10 12:04               ` Nikolay Borisov
2018-03-10 14:29                 ` Christoph Anton Mitterer
2018-03-11 17:51                   ` Goffredo Baroncelli [this message]
2018-03-11 22:37                     ` Christoph Anton Mitterer
2018-03-12 21:22                       ` Goffredo Baroncelli
2018-03-12 21:48                         ` Christoph Anton Mitterer
2018-03-13 19:36                           ` Goffredo Baroncelli
2018-03-13 20:10                             ` Christoph Anton Mitterer
2018-03-14 12:02                             ` Austin S. Hemmelgarn
2018-03-14 18:39                               ` Goffredo Baroncelli
2018-03-14 19:27                                 ` Austin S. Hemmelgarn
2018-03-14 22:17                                   ` Goffredo Baroncelli
2018-03-13 13:47               ` Patrik Lundquist
2018-03-02  4:02     ` Qu Wenruo

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