[libvirt] [PATCH 4/4] qemu: snapshot: Add support for compressing external snapshot memory

[Peter Krempa]

On 10/09/13 18:38, Daniel P. Berrange wrote:
> On Wed, Oct 09, 2013 at 06:31:32PM +0200, Peter Krempa wrote:
>> The regular save image code has the support to compress images using a
>> specified algorithm. This was not implemented for external checkpoints
>> although it shares most of the backend code.
>>
>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1017227
>> ---
>>  src/qemu/qemu.conf     |  6 ++++++
>>  src/qemu/qemu_conf.c   |  1 +
>>  src/qemu/qemu_conf.h   |  1 +
>>  src/qemu/qemu_driver.c | 23 +++++++++++++++++++++--
>>  4 files changed, 29 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
>> index 7cf67df..aff5e6d 100644
>> --- a/src/qemu/qemu.conf
>> +++ b/src/qemu/qemu.conf
>> @@ -283,9 +283,15 @@
>>  # specified format isn't valid, or the requested compression program can't be
>>  # found.
>>  #
>> +# snapshot_image_format specifies the compression algorithm of the memory save
>> +# image when an external snapshot of a domain is taken. This does not apply
>> +# on disk image format. It is an error if the specified format isn't valid,
>> +# or the requested compression program can't be found.
>> +#
>>  #save_image_format = "raw"
>>  #dump_image_format = "raw"
>>  #managedsave_image_format = "raw"
>> +#snapshot_image_format = "raw"
> 
> Same question here as previous patch. A snapshot is really just another
> form of saved image.

Here I have a bit stronger opinion compared to the managedsave case. I
really think that users might prefer different settings for snapshots
especially that snapshots can be created with a live guest, where a
compression algorithm may inhibit successful finish of creating a
snapshot as the migration procedure will be too slow to accomodate
changing a lot of pages in the guest memory. Thus it might be desired to
store snapshots uncompressed or just with a quick algorithm.

The second option would be to disable compression for live snapshots,
but that might be unfortunate too.

> 
> Daniel
> 

Peter


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