Re: [Qemu-block] Restoring bitmaps after failed/cancelled migration

[Vladimir Sementsov-Ogievskiy]

16.05.2018 15:47, Kevin Wolf wrote:
> Am 14.05.2018 um 12:09 hat Vladimir Sementsov-Ogievskiy geschrieben:
> > 14.05.2018 09:41, Fam Zheng wrote:
> > > On Wed, 04/18 17:00, Vladimir Sementsov-Ogievskiy wrote:
> > > > Is it possible, that target will change the disk, and then we return control
> > > > to the source? In this case bitmaps will be invalid. So, should not we drop
> > > > all the bitmaps on inactivate?
> > > Yes, dropping all live bitmaps upon inactivate sounds reasonable. If the dst
> > > fails to start, and we want to resume VM at src, we could (optionally?) reload
> > > the persistent bitmaps, I guess.
> > Reload from where? We didn't store them.
> Maybe this just means that it turns out that not storing them was a bad
> idea?
>
> What was the motivation for not storing the bitmap? The additional
> downtime? Is it really that bad, though? Bitmaps should be fairly small
> for the usual image sizes and writing them out should be quick.
>
> Kevin

What are usual ones? A bitmap of standard granularity of 64k for 16Tb 
disk is ~30mb. If we have several such bitmaps it may be significant 
downtime.



--
Best regards,
Vladimir