From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: misunderstanding of spare and raid devices? - and one question more Date: Fri, 1 Jul 2011 07:28:55 +1000 Message-ID: <20110701072855.69ee763b@notabene.brown> References: <4E0C5539.4030000@gmx.de> <4E0C5E47.5090604@anonymous.org.uk> <4E0C6CC4.3030506@turmel.org> <4E0C7196.1070307@gmx.de> <4E0C7B4B.7090404@turmel.org> <4E0C8685.3020806@gmx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4E0C8685.3020806@gmx.de> Sender: linux-raid-owner@vger.kernel.org To: Karsten =?ISO-8859-1?B?UvZta2U=?= Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, 30 Jun 2011 16:21:57 +0200 Karsten R=F6mke wr= ote: > Hi Phil > > > > If your CPU has free cycles, I suggest you run raid6 instead of rai= d5+spare. > > > > Phil > > > I started the raid 6 array and get: >=20 > Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] > md0 : active raid6 sde5[4] sdd5[3] sdc5[2] sdb2[1] sda3[0] > 13759296 blocks level 6, 64k chunk, algorithm 2 [5/5] [UUUUU] > [=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D>...] res= ync =3D 87.4% (4013184/4586432) finish=3D0.4min speed=3D20180K/sec ^^^^^^ Note: resync >=20 > when I started the raid 5 array I get >=20 > md0 : active raid5 sdd5[4] sde5[5](S) sdc5[2] sdb2[1] sda3[0] > 13759296 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_] > [=3D>...................] recovery =3D 6.2% (286656/4586432)= finish=3D0.9min speed=3D71664K/sec ^^^^^^^^ Note: recovery. >=20 > so I have to expect a three times less write speed - or is this calcu= lation > to simple ? >=20 You are comparing two different things, neither of which is write speed= =2E If you want to measure write speed, you should try writing and measure = that. When you create a RAID5 mdadm deliberately triggers recovery rather tha= n resync as it is likely to be faster. This is why you see a missed devi= ce and an extra spare. I don't remember why it doesn't with RAID6. NeilBrown -- 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