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Re: [dm-devel] [PATCH 26/30] ext4: do not send discards as barriers



On Tue 31-08-10 00:39:41, Vladislav Bolkhovitin wrote:
> Jan Kara, on 08/31/2010 12:20 AM wrote:
> >On Mon 30-08-10 15:56:43, Jeff Moyer wrote:
> >>Jan Kara<jack suse cz>  writes:
> >>
> >>>   An update: I've set up an ext4 barrier testing in KVM - run fsstress,
> >>>kill KVM at some random moment and check that the filesystem is consistent
> >>>(kvm is run in cache=writeback mode to simulate disk cache). About 70 runs
> >>
> >>But doesn't your "disk cache" survive the "power cycle" of your guest?
> >   Yes, you're right. Thinking about it now the test setup was wrong because
> >it didn't refuse writes to the VM's data partition after the moment I
> >killed KVM. Thanks for catching this. I will probably have to use the fault
> >injection on the host to disallow writing the device at a certain moment.
> >Or does somebody have a better option?
> 
> Have you considered to setup a second box as an iSCSI target (e.g.
> with iSCSI-SCST)? With it killing the connectivity is just a matter
> of a single iptables command + a lot more options.
  Hmm, this might be an interesting option. Will try that. Thanks for
suggestion. 

								Honza
-- 
Jan Kara <jack suse cz>
SUSE Labs, CR


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