From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Baptiste Thomas Subject: Re: Paranoid mode for RAID-1 ? Date: Mon, 27 Apr 2015 12:52:03 +0200 (CEST) Message-ID: <1670710921.23079769.1430131923662.JavaMail.zimbra@laposte.net> References: <1610581828.22506051.1430116628556.JavaMail.zimbra@laposte.net> <972437107.22507366.1430116679975.JavaMail.zimbra@laposte.net> <20150427164924.2aee3831@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20150427164924.2aee3831@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 2015-04-27 16:49 +1000, NeilBrown wrote: > On Mon, 27 Apr 2015 08:37:59 +0200 (CEST) Jean-Baptiste Thomas > wrote: >=C2=B7 > > I'm looking for a way to get MD to operate in a mode in which > > reading a sector from a RAID-1 device would not succeed until it > > got matching data from at least two components. >=C2=B7 > No, there is no such thing. Thanks, now I can move on to working on plan B. =20 > There "should" be no circumstance which would make it worth while. > A drive may well report an error, but it should *never* report > incorrect data as though it were correct. That is horribly > broken. Isn't it. > The cost of running in a "safe" mode would be high, and the > likely benefit extremely low. So it is unlikely that anyone > would use it for long. So implementing it seems rather > pointless. How high would the cost be ?=20 Seems to me that a 4-component RAID-1 with a 2-component quorum would incur no more I/O or CPU overhead than, say, a 4-component RAID-6. Less, in fact, unless parity computation is faster than memcmp().=20 Given the choice between that sort of cost and the possibility of massive data corruption because one drive had a hiccup, I would not even THINK about running without it. > That said: if someone were to provide an implementation I=20 > would certainly consider reviewing it and adding it to md. Great. Don't think it'll be me, though. :-/ -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html