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Date: Thu, 20 Aug 2015 21:26:09 -0600
From: "Nick Wang" <nwang@suse.com>
To: "Lars Ellenberg" <lars.ellenberg@linbit.com>
Cc: "Philipp Reisner" <philipp.reisner@linbit.com>,
        <drbd-dev@lists.linbit.com>, <linux-kernel@vger.kernel.org>
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Hi Lars,

> I still think this does not belong into the kernel at all.
> I may not yet have properly explained why.
> 
   Thanks for your information. 
   I tried blkdiscard on my test machine, but unfortunately the 
underlying block device i used doesn't support discard...
(/sys/block/<dev>/queue/discard_max_bytes == 0)
However, i think blkscard could work well for SSDs and 
thinly-provisioned support storage as a workaround.

> This is a lot of stuff to add to the DRBD module,
> introducing write protocol incompatibility/protocol version bump.
> 
> For no good reason.
> 
  Yes, it is not a mandatory feature, more like a enhancement 
"convenience patch" for some edge cases. User can choose 
zeroout/discard devices via drbd tools, in case the storage
does not support discard, it will using zeroout instead of only 
throw an "not support" error to output.

  Implement this function to drbd also help to sync the status 
between nodes, convenience for auto deploy or monitor by admin.
Also have the possibility to implement a resume broken 
zeroout/discard in future.

  And i can understand your concern and any decision, many thanks 
for your and Philipp's help and review:)

Best regards,
Nick 

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