From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-afa66.mailout.artfiles.de ([212.72.176.66]:41864 "EHLO mailout-afa66.mailout.artfiles.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752617AbcHMP43 (ORCPT ); Sat, 13 Aug 2016 11:56:29 -0400 Received: from [88.70.41.116] (helo=discus.localnet) auth=Wolfgang_Mader@brain-frog.de by mailout.artfiles.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80.1) id 1bYb1u-0002ud-KJ for linux-btrfs@vger.kernel.org; Sat, 13 Aug 2016 17:39:22 +0200 From: Wolfgang Mader To: Btrfs BTRFS Subject: Likelihood of read error, recover device failure raid10 Date: Sat, 13 Aug 2016 17:39:18 +0200 Message-ID: <2336793.AMaAIAxWk4@discus> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2053457.9v2q7TCjBG"; micalg="pgp-sha256"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --nextPart2053457.9v2q7TCjBG Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Hi, I have two questions 1) Layout of raid10 in btrfs btrfs pools all devices and than stripes and mirrors across this pool. Is it therefore correct, that a raid10 layout consisting of 4 devices a,b,c,d is _not_ raid0 |---------------| ------------ ------------- |a| |b| |c| |d| raid1 raid1 Rather, there is no clear distinction of device level between two devices which form a raid1 set which are than paired by raid0, but simply, each bit is mirrored across two different devices. Is this correct? 2) Recover raid10 from a failed disk Raid10 inherits its redundancy from the raid1 scheme. If I build a raid10 from n devices, each bit is mirrored across two devices. Therefore, in order to restore a raid10 from a single failed device, I need to read the amount of data worth this device from the remaining n-1 devices. In case, the amount of data on the failed disk is in the order of the number of bits for which I can expect an unrecoverable read error from a device, I will most likely not be able to recover from the disk failure. Is this conclusion correct, or am I am missing something here. Thanks, Wolfgang --nextPart2053457.9v2q7TCjBG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJXrz8mAAoJEGZtonfLCdqhuOkQAJKCPmk52fK8uL+5QAk5p92s JtVj0hyhbrM4M/YedUkFfAEXhdh8GA7Owr+al9O1FRxjriGham2Lej5JaN/kZ+/s NJkR1hesUFsfwAL6z3E0ZXNIMH1NP5IUVPsNcv90+dTvrrbv332hScTf6Klc7yc+ blO4LNqwF/k120+Kgm8d2xOolwkc+9kfi+TM+ntGtvcQVGltVjQcjwmeJ2+olpTg MzwAW6sU73MB76Fo8nFtxygCySz//d/l4ePy61shXUWiQIjaIAG3bmf5y4e84hDh 5tnLinj4wOHSxXliCNMjL5RN94bt6+OwTJK0pmhpSx+5Hf8LUTJKeVxkcmKorYFF 3TOaPuJsp26H/eqF36e5WSnJ6jBKaJGKazWvX42QyFxYuuBqd0qXdeoEloWmTyLa ebz48IUWMMoT/Vx5XXwfBWkm/V3crOP1ua96QCISp7SB2Xy5IXR9Ju7NEx5/npIx +vNSevrbPdTCMaf0OYyd/h1oVGsPuMSmHRbgN1BxYFvfHr6G3fjH77iRw3iIUA+y dY+q1MDG/xPpKo/OCNO8t+Hss8DeXQ7j/N2UWHSdLorS6/VOdRrNKfH7/IiL+I73 B10KoFmWSniJxRGb901ND6YGFxb/qViZISfm+L7CMZqZXhC/9WZ0hyxotRRMvpsz DXTdqyULQZ4IpSqevhON =8FdV -----END PGP SIGNATURE----- --nextPart2053457.9v2q7TCjBG--