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Date:      Tue, 23 May 2023 20:26:27 +0300
From:      Vitaliy Gusev <gusev.vitaliy@gmail.com>
To:        Poul-Henning Kamp <phk@phk.freebsd.dk>
Cc:        virtualization@freebsd.org, freebsd-hackers@freebsd.org
Subject:   Re: BHYVE SNAPSHOT image format proposal
Message-ID:  <5544A8DA-4E91-4384-B72D-8C91B32B6D69@gmail.com>
In-Reply-To: <202305231645.34NGj2Bq081239@critter.freebsd.dk>
References:  <67FDC8A8-86A6-4AE4-85F0-FF7BEF9F2F06@gmail.com> <202305231645.34NGj2Bq081239@critter.freebsd.dk>

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Hi,

> On 23 May 2023, at 19:45, Poul-Henning Kamp <phk@phk.freebsd.dk> =
wrote:
>=20
>=20
>> 1. BHYVE SNAPSHOT image format:
>=20
> Please do not invent Yet Another Format, please ?
>=20
> Why not make it a tar(5) file ?
>=20

Tar cannot solve issues mentioned in =E2=80=9Cdisadvantages=E2=80=9D. =
Tar doesn=E2=80=99t have versions, it is just container for files
that would introduce another level of indirection. Snapshot/resume =
doesn=E2=80=99t need just container. It needs
information what is saved and in what format. For example, virtual =
memory can be saved in different ways: binary,
diff pages, etc.

Virtual memory of VM should be saved faster without additional cost. The =
same for restore stage. Do you like
an idea to have tar file with size 8 GB ? And how it can be saved =
efficiently without double copying of data?

Yes, tar is powerful and convenient for many purposes, but it is not so =
suitable to suspend/resume process and
would introduce just another level of complexity.

=E2=80=94=E2=80=94
Vitaliy Gusev=



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