From: Roman Mamedov <rm@romanrm.ru>
To: NeilBrown <neilb@suse.de>
Cc: linux-raid@vger.kernel.org
Subject: Re: [md PATCH 01/10] md: allow a reshape operation to be reversed.
Date: Mon, 1 Oct 2012 15:11:28 +0600 [thread overview]
Message-ID: <20121001151128.0a5e336f@natsu> (raw)
In-Reply-To: <20120403055301.19495.37242.stgit@notabene.brown>
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On Tue, 03 Apr 2012 15:53:01 +1000
NeilBrown <neilb@suse.de> wrote:
> Currently a reshape operation always progresses from the start
> of the array to the end unless the number of devices is being
> reduced, in which case it progressed in the opposite direction.
>
> To reverse a partial reshape which changes the number of devices
> you can stop the array and re-assemble with the raid-disks numbers
> reversed and it will undo.
>
> However for a reshape that does not change the number of devices
> it is not possible to reverse the reshape in the middle - you have to
> wait until it completes.
>
> So add a 'reshape_direction' attribute with is either 'forwards' or
> 'backwards' and can be explicitly set when delta_disks is zero.
>
> This will become more important when we allow the data_offset to
> change in a reshape. Then the explicit statement of what direction is
> being used will be more useful.
>
> This can be enabled in raid5 trivially as it already supports
> reverse reshape and just needs to use a different trigger to request it.
Hello,
Is it possible to use this to cancel a RAID5 reshape that is reducing the
number of devices?
I understand that reshape goes backwards by design in this case, so I need to
switch it to "forwards".
I stopped the reshaping array and then started it with "mdadm --assemble
--freeze-reshape" and listing the backup file and all the devices on the command line.
But even then:
# echo forwards > /sys/block/md0/md/reshape_direction
-bash: echo: write error: Device or resource busy
--
With respect,
Roman
~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Stallman had a printer,
with code he could not see.
So he began to tinker,
and set the software free."
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next prev parent reply other threads:[~2012-10-01 9:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-03 5:53 [md PATCH 00/10] md patches for 3.5: RAID10 reshape NeilBrown
2012-04-03 5:53 ` [md PATCH 01/10] md: allow a reshape operation to be reversed NeilBrown
2012-10-01 9:11 ` Roman Mamedov [this message]
2012-10-01 10:15 ` Roman Mamedov
2012-10-02 2:41 ` NeilBrown
2012-04-03 5:53 ` [md PATCH 04/10] md/raid5: allow for change in data_offset while managing a reshape NeilBrown
2012-04-03 5:53 ` [md PATCH 05/10] md/raid10: collect some geometry fields into a dedicated structure NeilBrown
2012-04-03 5:53 ` [md PATCH 06/10] md: teach sync_page_io about new_data_offset NeilBrown
2012-04-03 5:53 ` [md PATCH 02/10] md: add possibility to change data-offset for devices NeilBrown
2012-04-03 5:53 ` [md PATCH 03/10] md/raid5: Use correct data_offset for all IO NeilBrown
2012-04-03 5:53 ` [md PATCH 09/10] md/raid10: split out interpretation of layout to separate function NeilBrown
2012-04-03 5:53 ` [md PATCH 10/10] md/raid10: add reshape support NeilBrown
2012-04-03 5:53 ` [md PATCH 07/10] md: use resync_max_sectors for reshape as well as resync NeilBrown
2012-04-03 5:53 ` [md PATCH 08/10] md/raid10: Introduce 'prev' geometry to support reshape NeilBrown
2014-03-01 5:08 ` [md PATCH 00/10] md patches for 3.5: RAID10 reshape Phillip Susi
2014-03-01 7:03 ` NeilBrown
2014-03-01 19:33 ` Phillip Susi
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