From: Joe Thornber <thornber@redhat.com>
To: device-mapper development <dm-devel@redhat.com>
Subject: Re: all cache blocks marked as dirty in writethrough mode, "Data loss may occur", constant write activity
Date: Mon, 30 Jun 2014 12:25:13 +0100 [thread overview]
Message-ID: <20140630112513.GA3893@debian> (raw)
In-Reply-To: <20140630091403.GB3098@debian>
On Mon, Jun 30, 2014 at 10:14:03AM +0100, Joe Thornber wrote:
> - There's a constant 4k background load to the metadata device.
>
> I'll look into this. Sounds like the periodic commit is re writing
> the superblock even if there's no change to the mappings.
I've added this test to the dm test suite:
https://github.com/jthornber/device-mapper-test-suite/blob/master/lib/dmtest/tests/cache/io_use_tests.rb
Using my latest development tree I can't see any spurious IO.
I also instrumented to see exactly when the superblock is written,
again nothing happens while the cache is idle. So I'm puzzled about
what you are seeing.
- Joe
prev parent reply other threads:[~2014-06-30 11:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-28 22:54 all cache blocks marked as dirty in writethrough mode, "Data loss may occur", constant write activity Marc Lehmann
2014-06-30 9:14 ` Joe Thornber
2014-06-30 11:25 ` Joe Thornber [this message]
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