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From: Phil Turmel <philip@turmel.org>
To: David Waite <david@alkaline-solutions.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Unable to (un)-grow raid6
Date: Sun, 6 Dec 2015 16:21:38 -0500	[thread overview]
Message-ID: <5664A6E2.4070900@turmel.org> (raw)
In-Reply-To: <9F08EE4D-B926-4F8F-9F9D-F9C7234959B4@alkaline-solutions.com>

On 12/06/2015 04:13 PM, David Waite wrote:
> 
>> On Dec 6, 2015, at 1:35 PM, Phil Turmel <philip@turmel.org> wrote:
>>
>> On 12/05/2015 10:04 PM, David Waite wrote:
>>> I’m having difficulty shrinking down a RAID6 array (md2) on a Sinology NAS. I wish to go from 13 drives to 11, and believe I need to go to 12 first to maintain operation and redundancy through the resizing process.
>>
>> No, you can go straight to 11 if you've set array-size properly.  --grow
>> operations maintain redundancy throughout.
> 
> I thought —grow maintains redundancy for power loss but not disk failure.
> 
> Would I do this by simply marking the other drive I want to remove as failed?

No!  Is that what you did with the other one?

--grow with a reduction in number leaves the unneeded drive(s) as hot
spares when it is complete.  That's when you remove them.  Or, if it
didn't pick the drives you wanted to remove, you can then do a --replace
operation, which also maintains redundancy throughout.

> I’ll try —array-size again. How is the array-size suggestion by mdadm calculated - the drives are not of uniform size.

You didn't post your --detail and --examine output as requested, so I
can't be specific.  For parity arrays, the size of the smallest member
controls the size of the array.

Phil
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  reply	other threads:[~2015-12-06 21:21 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <4E26C335-DEDB-489E-B54E-A285273569A1@alkaline-solutions.com>
2015-12-06  3:04 ` Unable to (un)-grow raid6 David Waite
2015-12-06 20:35   ` Phil Turmel
2015-12-06 21:13     ` David Waite
2015-12-06 21:21       ` Phil Turmel [this message]
     [not found]         ` <BACF203A-3817-4F24-88B0-38713D9459D9@alkaline-solutions.com>
     [not found]           ` <5664D042.9080401@turmel.org>
     [not found]             ` <10980501-F73B-4A63-AF7D-D7100C9C6B72@alkaline-solutions.com>
2015-12-09  3:12               ` Phil Turmel

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