From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: RE: mismatch_cnt > 0 during initial sync? Date: Wed, 21 Jun 2017 07:26:11 +1000 Message-ID: <87bmpi2vws.fsf@notabene.neil.brown.name> References: <9A8A3C34-EED0-42FF-B631-7AD1D6EAF9A2@stanford.edu> <87shix3rpi.fsf@notabene.neil.brown.name> <009901d2e946$a3eff400$ebcfdc00$@wnsdev.com> <87lgon2t30.fsf@notabene.neil.brown.name> <002e01d2ea03$232cb660$69862320$@wnsdev.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Return-path: In-Reply-To: <002e01d2ea03$232cb660$69862320$@wnsdev.com> Sender: linux-raid-owner@vger.kernel.org To: Peter Sangas , 'Stephane Thiell' , linux-raid@vger.kernel.org List-Id: linux-raid.ids --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Tue, Jun 20 2017, Peter Sangas wrote: >> From: NeilBrown [mailto:neilb@suse.com] >> Sent: Monday, June 19, 2017 9:15 PM >> Subject: RE: mismatch_cnt > 0 during initial sync? >>=20 >> This is a recovery, not a resync. They are different. >=20=20 > Thank you for pointing this out and the nice explanation.=20=20=20=20 > > From reading this list and other sources issuing a repair command as > follows: > > "echo repair > /sys/block/md2/md/sync_action" > > might be ill-advised since it's luck of the draw whether or not the > operation gets the right data instead of the bad data. > > Is this correct?=20 How do you define "right data" and "bad data"? What is your threat-model which explains how the two blocks are different? In most likely cases, neither version if the data is more correct than the other. In some others, your hardware is broken and needs to be replaced. If you have no understanding of why there might be a difference, then issuing a repair is not likely to be worse than not issuing a repair. If you do have that understanding, then use that to make your decision. NeilBrown > > For reference I have a RAID1 with 3 disks. mdadm - v3.3 - 3rd September > 2013 > > Thank you, > Pete --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAllJkvQACgkQOeye3VZi gbmHjw/9H4X6ePzsWmlAug/CDWOtGNlXaMazOkb6uATOqKcMLRfWC7AQH/u3XHky /7CgRRXVrFou7I+gGNb1NTqXhb5tSMZcn7p1w47zIwOnIc/weVjFq1Xl6VFdg/DR vQrrKVw73/p+gwEAhLcBvC169g7IDA17dLH9UzhYfnCuZ/hgVSTaQ41AtdDY0iKp bCz1TOwnthRktG9ORaqiIHodN6Dabl/Q+SXG7/T4A90oQMU87OSv9xLPLqoYjUcb 7YpxgOFnXR9vZBntciOxvMBNHfbtO3Tlo8yZB3FtuWd9+H9fRj1tnkj3JnFpLph6 zen93TPO/1AL8BDWI5w3bROon99Ni41iCmFg2QbI5PRYj2Gnsx+RTm66injaOjQD Oh6lYetUmbS+7a9xL/D1uP4uhkbFAA/7RG8qhC0pD1ORxtjm9gFrYMEh5P0qreiv 7qx2Tr9IGJCkMci7xOwZtlHZ/FaQHiKwCvNDk6pHNiITSuMFHTom8b/JAM+Z1Wpf qOo/RaFnPDQifbQKwtLdnXgJIhiA1JSCqS9wex5oLAfUovS5F5SsiIWlDloPs4Gm yCEieOPtryb4ZCkywyR43SL2nFTOH6QqBg4K2DdlpEPxVz2gW7LmMiVOYp9a/GEM O2s//t6g8n434TUqmkyR1EYCou0vqe9jXFqBMpiX5u/qGCb9txY= =FBY1 -----END PGP SIGNATURE----- --=-=-=--