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

[Vladislav Bolkhovitin]

Jan Kara, on 08/31/2010 12:20 AM wrote:
> On Mon 30-08-10 15:56:43, Jeff Moyer wrote:
>> Jan Kara<jack at 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.

Vlad