From: Dushyant Bansal <cs5070214@cse.iitd.ac.in>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Re: KVM call agenda for Jan 25
Date: Mon, 14 Mar 2011 20:43:31 +0530 [thread overview]
Message-ID: <4D7E309B.6080800@cse.iitd.ac.in> (raw)
In-Reply-To: <AANLkTimMyCmy6yYJM6+5QdAt0DjCQq=WHE1iOwpJJHAq@mail.gmail.com>
>
> Nice that qemu-img convert isn't that far out by default on raw :).
>
> About Google Summer of Code, I have posted my take on applying and
> want to share that with you and qemu-devel:
>
> http://blog.vmsplice.net/2011/03/advice-for-students-applying-to-google.html
>
Thanks for sharing your experiences.
After reading about qcow2 and qed and how they organize data (thanks to
the newly added qcow2 doc and discussions on the mailing list), this is
what I understand.
So, the main difference between qed and qcow2 is the absence of
reference count structure in qed(means less meta data).
It improves performance due to:
1. For write operations, less or no metadata to update.
2. Data write and metadata write can be in any order
This also means these features are no longer supported:
1. Internal snapshots,
2. CPU/device state snapshots,
3. Compression,
4. Encryption
Now, coming to qed<-->qcow2 conversion, I want to clarify some things.
1. header_size: variable in qed, equals to cluster size in qcow2:
When will it be larger than 1 cluster in qed? So, what will happen to
that extra data on qed->qcow2 conversion.
2. L2 table size: equals to L1 table size in qed, equals to cluster size
in qcow2:
we need to take it into account during conversion.
3. refcount table:
qcow2->qed:we do not keep refcount structure
qed->qcow2: initialize refcount structure
So, a qcow2->qed->qcow2 conversion means if earlier, qcow2 image was
using additional features{1-4}, all information related to that will be
lost.
What do you think? Please correct me if I am making some incorrect
statement.
Thanks,
Dushyant
next prev parent reply other threads:[~2011-03-14 15:14 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-24 13:25 KVM call agenda for Jan 25 Chris Wright
2011-01-24 13:25 ` [Qemu-devel] " Chris Wright
2011-01-24 22:06 ` Anthony Liguori
2011-01-24 22:06 ` [Qemu-devel] " Anthony Liguori
2011-01-25 13:57 ` Luiz Capitulino
2011-01-25 14:02 ` Luiz Capitulino
2011-01-25 14:13 ` Stefan Hajnoczi
2011-01-25 14:13 ` Stefan Hajnoczi
2011-01-29 10:50 ` Dushyant Bansal
2011-01-29 13:16 ` Stefan Hajnoczi
2011-02-25 17:42 ` Dushyant Bansal
2011-02-26 14:05 ` Stefan Hajnoczi
2011-02-26 21:50 ` Dushyant Bansal
2011-02-27 10:49 ` Stefan Hajnoczi
2011-02-28 7:36 ` Markus Armbruster
2011-02-28 20:41 ` Dushyant Bansal
2011-03-01 9:40 ` Stefan Hajnoczi
2011-03-14 15:13 ` Dushyant Bansal [this message]
2011-03-15 10:27 ` Kevin Wolf
2011-03-16 14:17 ` Dushyant Bansal
2011-03-16 17:47 ` Stefan Hajnoczi
2011-03-17 10:07 ` Kevin Wolf
2011-03-26 21:56 ` Dushyant Bansal
2011-03-28 10:26 ` Kevin Wolf
2011-01-25 14:11 ` Aurelien Jarno
2011-01-25 14:11 ` Aurelien Jarno
2011-01-25 14:27 ` Anthony Liguori
2011-01-25 14:27 ` Anthony Liguori
2011-01-25 14:42 ` Kevin Wolf
2011-01-25 14:42 ` Kevin Wolf
2011-01-25 15:29 ` Aurelien Jarno
2011-01-25 14:26 ` Avi Kivity
2011-01-25 14:26 ` [Qemu-devel] " Avi Kivity
2011-01-25 14:35 ` Stefan Hajnoczi
2011-01-25 14:35 ` [Qemu-devel] " Stefan Hajnoczi
2011-01-26 9:58 ` Avi Kivity
2011-01-26 9:58 ` [Qemu-devel] " Avi Kivity
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