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From:   Phillip Susi <phill@thesusis.net>
To:     antlists <antlists@youngman.org.uk>
Cc:     Brian Allen Vanderburg II <brianvanderburg2@aim.com>,
        linux-raid@vger.kernel.org
Subject: Re: Linux raid-like idea
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Date:   Mon, 14 Sep 2020 13:19:24 -0400
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antlists writes:

> Yup. Raid 6 has two parity disks, and that's mirrored to give four 
> parity disks. So as an *absolute* *minimum*, raid-61 could lose four 
> disks with no data loss.

Don't you mean 5 disks?

At best 4 lost disks paird off in each raid1 means the raid6 sees two
failures.  One more disk failing isn't enough to take out another mirror
so the raid6 keeps ticking.