From: Loic Dachary <loic@dachary.org>
To: Gregory Farnum <greg@inktank.com>
Cc: Ceph Development <ceph-devel@vger.kernel.org>
Subject: Re: crc32 for erasure code
Date: Mon, 23 Sep 2013 19:10:31 +0200 [thread overview]
Message-ID: <52407607.7040307@dachary.org> (raw)
In-Reply-To: <CAPYLRzib=_3JdtZdrAr0xHbAXCcR--ZJHX1cMR1oRvADBwpCWA@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1570 bytes --]
On 23/09/2013 18:59, Gregory Farnum wrote:
> On Mon, Sep 23, 2013 at 1:34 AM, Loic Dachary <loic@dachary.org> wrote:
>> Hi,
>>
>> Unless I'm mistaken, ceph_crc32() is currently used in master via the crc32c() method of bufferlist to:
>>
>> * encode_with_checksum/decode_with_checksum a PGLog entry
>> * Message::decode_message/Message::encode_message a message via calc_*_crc
>> * FileJournal::do_read_entry/FileJournal::prepare_single_write a journal entry
>> * for information in the report monitory command ( Monitor.cc )
>>
>> Erasure coded chunks ( i.e. files ) will need checksums. Should this be implemented as an optional feature in ceph/src/os/FileStore.{h,cc} ? If the underlying filesystem does not provide this feature, FileStore would call ceph_crc32 each time the object is modified. A verification method would be exposed and used when scrubbing erasure coded pools.
>
> You mean should checksums be optional in the FileStore, or should we
> provide a plugin framework for using things other than crc32, or...?
> :)
Not really. I was under the impression that crc32 is good enough. I'm not sure where ( in the code path ) it should be used for erasure coded pools. In the FileStore ? Or in the erasure code PG to set an attribute of the object ? The FileStore seems to be more sensible but ... I'm not sure hence the mail ;-)
> -Greg
> Software Engineer #42 @ http://inktank.com | http://ceph.com
>
--
Loïc Dachary, Artisan Logiciel Libre
All that is necessary for the triumph of evil is that good people do nothing.
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 261 bytes --]
next prev parent reply other threads:[~2013-09-23 17:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-23 8:34 crc32 for erasure code Loic Dachary
2013-09-23 16:59 ` Gregory Farnum
2013-09-23 17:10 ` Loic Dachary [this message]
2013-09-23 17:14 ` Gregory Farnum
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=52407607.7040307@dachary.org \
--to=loic@dachary.org \
--cc=ceph-devel@vger.kernel.org \
--cc=greg@inktank.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.