From: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>
To: dsterba@suse.cz, Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH] btrfs: Allow more disks missing for RAID10
Date: Thu, 25 Jul 2019 15:14:05 -0400 [thread overview]
Message-ID: <bad64044-5168-848e-1799-6c621ae2337f@gmail.com> (raw)
In-Reply-To: <20190725183741.GX2868@twin.jikos.cz>
On 2019-07-25 14:37, David Sterba wrote:
> On Thu, Jul 18, 2019 at 02:27:49PM +0800, Qu Wenruo wrote:
>> RAID10 can accept as much as half of its disks to be missing, as long as
>> each sub stripe still has a good mirror.
>
> Can you please make a test case for that?
>
> I think the number of devices that can be lost can be higher than a half
> in some extreme cases: one device has copies of all stripes, 2nd copy
> can be scattered randomly on the other devices, but that's highly
> unlikely to happen.
It is possible, but as you mention highly unlikely. It's also possible
with raid1 mode too, and a lot less unlikely there (in fact, it's almost
guaranteed to happen in certain configurations).
>
> On average it's same as raid1, but the more exact check can potentially
> utilize the stripe layout.
>
next prev parent reply other threads:[~2019-07-25 19:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 6:27 [PATCH] btrfs: Allow more disks missing for RAID10 Qu Wenruo
2019-07-25 18:37 ` David Sterba
2019-07-25 19:14 ` Austin S. Hemmelgarn [this message]
2019-07-25 23:41 ` Qu Wenruo
2019-07-26 10:39 ` David Sterba
2019-07-31 6:58 ` Qu Wenruo
2019-07-31 13:23 ` David Sterba
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