From: Igor Fedotov <ifedotov@mirantis.com>
To: Sage Weil <sage@newdream.net>, Allen Samuels <Allen.Samuels@sandisk.com>
Cc: ceph-devel <ceph-devel@vger.kernel.org>
Subject: Re: Adding compression/checksum support for bluestore.
Date: Thu, 31 Mar 2016 19:27:24 +0300 [thread overview]
Message-ID: <56FD4FEC.4060000@mirantis.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1603301806380.22014@cpach.fuggernut.com>
On 31.03.2016 1:15, Sage Weil wrote:
> On Wed, 30 Mar 2016, Allen Samuels wrote:
>> [snip]
>>
>> Time to talk about checksums.
>>
>> First let's divide the world into checksums for data and checksums for
>> metadata -- and defer the discussion about checksums for metadata
>> (important, but one at a time...)
>>
>> I believe it's a requirement that when checksums are enabled that 100%
>> of data reads must be validated against their corresponding checksum.
>> This leads you to conclude that you must store a checksum for each
>> independently readable piece of data.
> I'm just worried about the size of metadata if we have 4k checksums but
> have to read big extents anyway; cheaper to store a 4 byte checksum for
> each compressed blob.
But do we really need to store checksums as metadata?
What's about pre(post)fixing 4K-4(?) blob with the checksum and store
this pair to the disk.
IMO we always need checksum values along with blob data thus let's store
and read them together.
This immediately eliminates the question about the granularity and
corresponding overhead...
Have I missed something?
next prev parent reply other threads:[~2016-03-31 16:27 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-30 19:46 Adding compression/checksum support for bluestore Allen Samuels
2016-03-30 20:41 ` Vikas Sinha-SSI
2016-03-30 22:24 ` Sage Weil
2016-03-30 22:35 ` Allen Samuels
2016-03-31 16:31 ` Igor Fedotov
2016-03-30 22:15 ` Sage Weil
2016-03-30 22:22 ` Gregory Farnum
2016-03-30 22:30 ` Sage Weil
2016-03-30 22:43 ` Allen Samuels
2016-03-30 22:32 ` Allen Samuels
2016-03-30 22:52 ` Allen Samuels
2016-03-30 22:57 ` Sage Weil
2016-03-30 23:03 ` Gregory Farnum
2016-03-30 23:08 ` Allen Samuels
2016-03-31 23:02 ` Milosz Tanski
2016-04-01 3:56 ` Chris Dunlop
2016-04-01 4:56 ` Sage Weil
2016-04-01 5:28 ` Chris Dunlop
2016-04-01 14:58 ` Sage Weil
2016-04-01 19:49 ` Chris Dunlop
2016-04-01 23:08 ` Allen Samuels
2016-04-02 2:23 ` Allen Samuels
2016-04-02 2:51 ` Gregory Farnum
2016-04-02 5:05 ` Chris Dunlop
2016-04-02 5:48 ` Allen Samuels
2016-04-02 6:18 ` Gregory Farnum
2016-04-03 13:27 ` Sage Weil
2016-04-04 15:33 ` Chris Dunlop
2016-04-04 15:51 ` Chris Dunlop
2016-04-04 17:58 ` Allen Samuels
2016-04-04 15:26 ` Chris Dunlop
2016-04-04 17:56 ` Allen Samuels
2016-04-02 5:08 ` Allen Samuels
2016-04-02 4:07 ` Chris Dunlop
2016-04-02 5:38 ` Allen Samuels
2016-04-04 15:00 ` Chris Dunlop
2016-04-04 23:58 ` Allen Samuels
2016-04-05 12:35 ` Sage Weil
2016-04-05 15:10 ` Chris Dunlop
2016-04-06 6:38 ` Chris Dunlop
2016-04-06 15:47 ` Allen Samuels
2016-04-06 17:17 ` Chris Dunlop
2016-04-06 18:06 ` Allen Samuels
2016-04-07 0:43 ` Chris Dunlop
2016-04-07 0:52 ` Allen Samuels
2016-04-07 2:59 ` Chris Dunlop
2016-04-07 9:51 ` Willem Jan Withagen
2016-04-07 12:21 ` Atchley, Scott
2016-04-07 15:01 ` Willem Jan Withagen
2016-04-07 9:51 ` Chris Dunlop
2016-04-08 23:16 ` Allen Samuels
2016-04-05 20:41 ` Allen Samuels
2016-04-05 21:14 ` Sage Weil
2016-04-05 12:57 ` Dan van der Ster
2016-04-05 20:50 ` Allen Samuels
2016-04-06 7:15 ` Dan van der Ster
2016-03-31 16:27 ` Igor Fedotov [this message]
2016-03-31 16:32 ` Allen Samuels
2016-03-31 17:18 ` Igor Fedotov
2016-03-31 17:39 ` Piotr.Dalek
2016-03-31 18:44 ` Allen Samuels
2016-03-31 16:58 ` Igor Fedotov
2016-03-31 18:38 ` Allen Samuels
2016-04-04 12:14 ` Igor Fedotov
2016-04-04 14:44 ` Allen Samuels
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=56FD4FEC.4060000@mirantis.com \
--to=ifedotov@mirantis.com \
--cc=Allen.Samuels@sandisk.com \
--cc=ceph-devel@vger.kernel.org \
--cc=sage@newdream.net \
/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.