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From: Zdenek Kabelac <zkabelac@redhat.com>
To: lilofile <lilofile@aliyun.com>,
	device-mapper development <dm-devel@redhat.com>,
	Mike Snitzer <msnitzer@redhat.com>,
	Ondrej Kozina <okozina@redhat.com>,
	"Alasdair G. Kergon" <agk@redhat.com>
Subject: Re: reply： Thinly-Provisioned Logical Volumes
Date: Wed, 24 Sep 2014 09:02:40 +0200	[thread overview]
Message-ID: <54226C90.4080305@redhat.com> (raw)
In-Reply-To: <ae586129-fc3a-41fe-8f2e-f3124c5ff58d@aliyun.com>

Dne 24.9.2014 v 04:11 lilofile napsal(a):
> When I test thinly-provisioned logical volumes,I use dd if=/dev/zero of=/dev/mapper/mythinvolume count=1 bs=4k
> I only write 4k data in mythinvolume.but In thin_map functions, I found there are really  4K data written,but I found more read IO,probably dozens of read io. who issue these IO?
>

Hi

I'd have guessed those I/O are likely metadata update related - at most every 
second metadata are synchronized to your metadata storage volume.
(Thin pool consists of _tdata data volume where provisioned chunks are located 
and _tmeta metadata volume).

And btw you could use tools like thin_dump  to explore how is your pool used,
which chunks belong to which volume, which are share and so on....

Regards

Zdenek

  reply	other threads:[~2014-09-24  7:02 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-20 14:19 Thinly-Provisioned Logical Volumes lilofile
2014-09-22  7:02 ` Zdenek Kabelac
2014-09-22 12:38 ` Mike Snitzer
2014-09-23 13:51 ` reply： " lilofile
2014-09-23 14:07   ` Zdenek Kabelac
2014-09-24  2:11   ` lilofile
2014-09-24  7:02     ` Zdenek Kabelac [this message]
2014-09-24  8:37     ` Joe Thornber

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