From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arkadiusz Miskiewicz Subject: Re: bitmap questions Date: Thu, 14 Oct 2010 08:00:38 +0200 Message-ID: <201010140800.38419.a.miskiewicz@gmail.com> References: <201010131824.53363.a.miskiewicz@gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Paul Clements Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thursday 14 of October 2010, Paul Clements wrote: > On Wed, Oct 13, 2010 at 12:24 PM, Arkadiusz Miskiewicz >=20 > wrote: > > I have a question on how bitmap works and what's shown in /proc/mds= tat, > > for example: > >=20 > > md2 : active raid10 sdc3[0] sdd3[3] sdb3[2] sda3[1] > > 60002560 blocks 64K chunks 2 near-copies [4/4] [UUUU] > > bitmap: 1/1 pages [4KB], 65536KB chunk > >=20 > > - 1 bitmap for 4096 chunks > >=20 > > - if it shows 0/1 pages [0KB] what does it actually mean? >=20 > If it's 0 pages then no resync. > I assume you mean 1/1 ? Ok, I thought differently since it's bitmap->pages - bitmap->missing_pa= ges=20 (thought that missing_pages =3D=3D dirty one). > > Does that mean that > > in case of resync it will resync _all_ 4096 chunks in that page or= only > > chunks that require that (for example 7 chunks) ? >=20 > It only resyncs what is dirty. A page dirty in the in-memory bitmap > does not mean ALL bits are dirty, just that the page is allocated. So there is no way to know in advance how much is going to be resynced = when=20 sudden reset would happen in that moment? Anyway good to know that 1 page setup also makes sense :) > -- > Paul --=20 Arkadiusz Mi=C5=9Bkiewicz PLD/Linux Team arekm / maven.pl http://ftp.pld-linux.org/ -- 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