From: Bart Van Assche <bart.vanassche@sandisk.com>
To: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Jens Axboe <axboe@fb.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"drbd-dev@lists.linbit.com" <drbd-dev@lists.linbit.com>
Subject: Re: [Drbd-dev] [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity
Date: Mon, 25 Apr 2016 11:48:30 -0700 [thread overview]
Message-ID: <571E667E.4080200@sandisk.com> (raw)
In-Reply-To: <2101862.7IMGIqiMZK@phil-dell-xps.local>
On 04/25/2016 09:42 AM, Philipp Reisner wrote:
> 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.
>>
>> 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?
>
> 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.
Hello Phil,
Are you aware that for aligned discard requests the discard granularity
does not affect the size of discard requests at all?
Regarding LVM volumes: if the discard granularity for such volumes can
change on the fly, shouldn't I/O be quiesced by the LVM kernel driver
before it changes the discard granularity? I think that increasing
discard granularity while I/O is in progress should be considered as a bug.
Bart.
next prev parent reply other threads:[~2016-04-25 19:04 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-25 12:07 [PATCH 00/30] DBRD updates Philipp Reisner
2016-04-25 12:07 ` [PATCH 01/30] drbd: bitmap bulk IO: do not always suspend IO Philipp Reisner
2016-04-25 12:07 ` [PATCH 02/30] drbd: change bitmap write-out when leaving resync states Philipp Reisner
2016-04-25 12:07 ` [PATCH 03/30] drbd: Kill code duplication Philipp Reisner
2016-04-25 12:07 ` [PATCH 04/30] drbd: Implement handling of thinly provisioned storage on resync target nodes Philipp Reisner
2016-04-25 15:28 ` [Drbd-dev] " Bart Van Assche
2016-04-25 16:21 ` Philipp Reisner
2016-04-25 12:07 ` [PATCH 05/30] drbd: Introduce new disk config option rs-discard-granularity Philipp Reisner
2016-04-25 15:35 ` [Drbd-dev] " Bart Van Assche
2016-04-25 16:21 ` Philipp Reisner
2016-04-25 18:48 ` Bart Van Assche [this message]
2016-04-25 19:49 ` Philipp Reisner
2016-04-25 20:37 ` Lars Ellenberg
2016-04-25 12:07 ` [PATCH 06/30] drbd: Create the protocol feature THIN_RESYNC Philipp Reisner
2016-04-25 12:07 ` [PATCH 07/30] drbd: adjust assert in w_bitmap_io to account for BM_LOCKED_CHANGE_ALLOWED Philipp Reisner
2016-04-25 12:07 ` [PATCH 08/30] drbd: fix regression: protocol A sometimes synchronous, C sometimes double-latency Philipp Reisner
2016-04-25 12:07 ` [PATCH 09/30] drbd: fix for truncated minor number in callback command line Philipp Reisner
2016-04-25 12:07 ` [PATCH 10/30] drbd: allow parallel flushes for multi-volume resources Philipp Reisner
2016-04-25 12:07 ` [PATCH 11/30] drbd: when receiving P_TRIM, zero-out partial unaligned chunks Philipp Reisner
2016-04-25 16:37 ` [Drbd-dev] " Bart Van Assche
2016-04-25 20:32 ` Lars Ellenberg
2016-04-25 21:23 ` Lars Ellenberg
2016-04-25 12:07 ` [PATCH 12/30] drbd: possibly disable discard support, if backend has discard_zeroes_data=0 Philipp Reisner
2016-04-25 12:07 ` [PATCH 13/30] drbd: zero-out partial unaligned discards on local backend Philipp Reisner
2016-04-25 12:07 ` [PATCH 14/30] drbd: allow larger max_discard_sectors Philipp Reisner
2016-04-25 12:07 ` [PATCH 15/30] drbd: finish resync on sync source only by notification from sync target Philipp Reisner
2016-04-25 12:07 ` [PATCH 16/30] drbd: introduce unfence-peer handler Philipp Reisner
2016-04-25 12:07 ` [PATCH 17/30] drbd: don't forget error completion when "unsuspending" IO Philipp Reisner
2016-04-25 12:07 ` [PATCH 18/30] drbd: if there is no good data accessible, writes should be IO errors Philipp Reisner
2016-04-25 12:07 ` [PATCH 19/30] drbd: only restart frozen disk io when D_UP_TO_DATE Philipp Reisner
2016-04-25 12:07 ` [PATCH 20/30] drbd: discard_zeroes_if_aligned allows "thin" resync for discard_zeroes_data=0 Philipp Reisner
2016-04-25 12:07 ` [PATCH 21/30] drbd: report sizes if rejecting too small peer disk Philipp Reisner
2016-04-25 12:07 ` [PATCH 22/30] drbd: introduce WRITE_SAME support Philipp Reisner
2016-04-25 12:07 ` [PATCH 23/30] drbd: sync_handshake: handle identical uuids with current (frozen) Primary Philipp Reisner
2016-04-25 12:07 ` [PATCH 24/30] drbd: disallow promotion during resync handshake, avoid deadlock and hard reset Philipp Reisner
2016-04-25 12:07 ` [PATCH 25/30] drbd: bump current uuid when resuming IO with diskless peer Philipp Reisner
2016-04-25 12:07 ` [PATCH 26/30] drbd: code cleanups without semantic changes Philipp Reisner
2016-04-25 12:07 ` [PATCH 27/30] drbd: get rid of empty statement in is_valid_state Philipp Reisner
2016-04-25 12:07 ` [PATCH 28/30] drbd: finally report ms, not jiffies, in log message Philipp Reisner
2016-04-25 12:07 ` [PATCH 29/30] drbd: al_write_transaction: skip re-scanning of bitmap page pointer array Philipp Reisner
2016-04-25 12:07 ` [PATCH 30/30] drbd: correctly handle failed crypto_alloc_hash Philipp Reisner
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