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Re: [Drbd-dev] [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity

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Am Montag, 25. April 2016, 08:35:26 schrieb Bart Van Assche:
> On 04/25/2016 05:10 AM, Philipp Reisner wrote:
> > As long as the value is 0 the feature is disabled. With setting
> > it to a positive value, DRBD limits and aligns its resync requests
> > to the rs-discard-granularity setting. If the sync source detects
> > all zeros in such a block, the resync target discards the range
> > on disk.
> 
> Hello Phil,
> 
> Can you explain why rs-discard-granularity is configurable instead of
> e.g. setting it to the least common multiple of the discard
> granularities of the underlying block devices at both sides?
> 
> Thanks,
> 

Hi Bart,

we had this idea as well. It seems that real world devices like larger
discards better than smaller discards. The other motivation was that
a device mapper logical volume might change it on the fly...
So we think it is best to delegate the decision on the discard chunk
size to user space.

best regards,
 Phil
	

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[PATCH 00/30] DBRD updates Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 04/30] drbd: Implement handling of thinly provisioned storage on resync target nodes Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
    Re: [Drbd-dev] [PATCH 04/30] drbd: Implement handling of thinly provisioned storage on resync target nodes Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 18:50 +0200
  [PATCH 15/30] drbd: finish resync on sync source only by notification from sync target Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 17/30] drbd: don't forget error completion when "unsuspending" IO Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
    Re: [Drbd-dev] [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 18:50 +0200
      Re: [Drbd-dev] [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 21:50 +0200
        [PATCH 05/30] drbd: Introduce new disk config option  rs-discard-granularity Lars Ellenberg <lars.ellenberg@linbit.com> - 2016-04-25 22:40 +0200
  [PATCH 28/30] drbd: finally report ms, not jiffies, in log message Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 11/30] drbd: when receiving P_TRIM, zero-out partial unaligned chunks Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
    [PATCH 11/30] drbd: when receiving P_TRIM, zero-out partial  unaligned chunks Lars Ellenberg <lars.ellenberg@linbit.com> - 2016-04-25 22:40 +0200
      Re: [PATCH 11/30] drbd: when receiving P_TRIM, zero-out partial  unaligned chunks Lars Ellenberg <lars.ellenberg@linbit.com> - 2016-04-25 23:30 +0200
  [PATCH 24/30] drbd: disallow promotion during resync handshake, avoid deadlock and hard reset Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 29/30] drbd: al_write_transaction: skip re-scanning of bitmap page pointer array Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200
  [PATCH 10/30] drbd: allow parallel flushes for multi-volume resources Philipp Reisner <philipp.reisner@linbit.com> - 2016-04-25 14:30 +0200

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