From: Chris Dunlop <chris@onthe.net.au>
To: Allen Samuels <Allen.Samuels@sandisk.com>
Cc: Sage Weil <sage@newdream.net>,
Igor Fedotov <ifedotov@mirantis.com>,
ceph-devel <ceph-devel@vger.kernel.org>
Subject: Re: Adding compression/checksum support for bluestore.
Date: Fri, 1 Apr 2016 14:56:11 +1100 [thread overview]
Message-ID: <20160401035610.GA5671@onthe.net.au> (raw)
In-Reply-To: <CY1PR0201MB189760F1BB3EB67EF216B71DE8980@CY1PR0201MB1897.namprd02.prod.outlook.com>
On Wed, Mar 30, 2016 at 10:52:37PM +0000, Allen Samuels wrote:
> One thing to also factor in is that if you increase the span of a
> checksum, you degrade the quality of the checksum. So if you go with 128K
> chunks of data you'll likely want to increase the checksum itself from
> something beyond a CRC-32. Maybe somebody out there has a good way of
> describing this quanitatively.
I would have thought the "quality" of a checksum would be a function of how
many bits it is, and how evenly and randomly it's distributed, and unrelated
to the amount of data being checksummed.
I.e. if you have any amount of data covered by an N-bit evenly randomly
distributed checksum, and "something" goes wrong with the data (or the
checksum), the chance of the checksum still matching the data is 1 in 2^n.
Cheers,
Chris
next prev parent reply other threads:[~2016-04-01 3:56 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 [this message]
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
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
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