From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Szecsei Subject: Re: Confusion with setting up new RAID6 with mdadm Date: Mon, 15 Nov 2010 20:01:48 +0200 Message-ID: <4CE1758C.5080008@geograph.co.za> References: <4CE00206.4000301@geograph.co.za> <20101115091326.42b38b84@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20101115091326.42b38b84@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, One last quick question: Neil Brown wrote: > Depending on which version of mdadm you are using, the default chunk = size > will be 64K or 512K. I would recommend using 512K even if you have a= n older > mdadm. 64K appears to be too small for modern hardware, particularly= if you > are storing large files. > > For raid6 with the current implementation it is safe to use "--assume= -clean" > to avoid the long recovery time. It is certainly safe to use that if= you > want to build a test array, do some performance measurement, and then= scrap > it and try again. If some time later you want to be sure that the ar= ray is > entirely in sync you can > echo repair> /sys/block/md0/md/sync_action > and wait a while. > =20 **************************************************** I have compiled the following mdadm on my Ubuntu 64 bit 10.04 Desktop=20 system: root@gs0:/home/geograph# uname -a Linux gs0 2.6.32-25-generic #45-Ubuntu SMP Sat Oct 16 19:52:42 UTC 2010= =20 x86_64 GNU/Linux root@gs0:/home/geograph# mdadm -V mdadm - v3.1.4 - 31st August 2010 root@gs0:/home/geograph# **************************************************** I have deleted the partitions on all 8 drives, and done a mdadm -Ss root@gs0:/home/geograph# fdisk -lu Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors Units =3D sectors of 1 * 512 =3D 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sda doesn't contain a valid partition table Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes ****************************************************** Based on the above "assume-clean" comment, plus all the help you guys=20 have offered, I have just run: mdadm --create /dev/md0 --metadata=3D1.2 --auto=3Dmd --assume-clean=20 --bitmap=3Dinternal --bitmap-chunk=3D131072 --chunk=3D512 --level=3D6=20 --raid-devices=3D8 /dev/sd[abcdefgh] It took a nano-second to complete! The man-pages for assume-clean say that "the array pre-existed". Surely= =20 as I have erased the HDs, and now have no partitions on them, this is=20 not true? Do I need to re-run the above mdadm command, or is it safe to proceed=20 with LVM then mkfs ext4? Thanks for all, Zoltan ****************************************************** root@gs0:/home/geograph# mdadm -E /dev/md0 mdadm: No md superblock detected on /dev/md0. root@gs0:/home/geograph# ls -la /dev/md* brw-rw---- 1 root disk 9, 0 2010-11-15 19:53 /dev/md0 /dev/md: total 0 drwxr-xr-x 2 root root 60 2010-11-15 19:53 . drwxr-xr-x 19 root root 4260 2010-11-15 19:53 .. lrwxrwxrwx 1 root root 6 2010-11-15 19:53 0 -> ../md0 root@gs0:/home/geograph# cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]=20 [raid4] [raid10] md0 : active raid6 sdc[2] sdf[5] sdh[7] sdd[3] sdb[1] sdg[6] sda[0] sde= [4] 11721077760 blocks super 1.2 level 6, 512k chunk, algorithm 2=20 [8/8] [UUUUUUUU] bitmap: 0/8 pages [0KB], 131072KB chunk unused devices: ******************************************************* --=20 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Zoltan Szecsei PrGISc [PGP0031] Geograph (Pty) Ltd. P.O. Box 7, Muizenberg 7950, South Africa. 65 Main Road, Muizenberg 7945 Western Cape, South Africa. 34=B0 6'16.35"S 18=B028'5.62"E Tel: +27-21-7884897 Mobile: +27-83-6004028 =46ax: +27-86-6115323 www.geograph.co.za =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1153 / Virus Database: 424/3258 - Release Date: 11/15/10 -- 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