Hi,
I hope this is the correct list to address this on - I've done a lot of
typing for nothing, if not :-)
I have done days of research, including reading
https://raid.wiki.kernel.org/index.php/Linux_Raid, but all I am doing is
getting confused in the detail.
My goal is to set up an 8*2TB SiI3132 based RAID6 on Ubuntu 10.04LTS,
with LVM and ext4.
The setup will mostly hold thousands of 400MB image files, and they will
not be accessed regularly - they mostly just need to be online. The
entire space on all 8 drives can be used, and I want 1 massive
filesystem, when I finally mount this RAID device. No boot, root or swap.
I have gone quite far with the help of the local linux group, but after
I had completed the 27 hour mdadm --create run, further tidbits were
thrown at me, and I am trying to get an opinion on if it is worth
scrapping this effort, and starting again.
Please can someone provide clarity on:
*If I have to reformat the drives and redo mdadm --create, other than
mdadm stop, how can I get rid of all the /dev/md* etc etc so that when I
restart this exercise, the original bad RAID does not interfere with
this new attempt?
*Partition alignment?
Is this relevant for modern HDs (I'm using 5900rpm Seagate 2TB drives)
None of the mdadm helps I've googled or received speak about how to
correctly format the drives before running mdadm --create.
All the benchmarks & performance tests I've found, do not bother to say
whether they have aligned the partitions on the HD
*What is the correct fdisk or parted method get rid of the DOS & GPT
flags, and create a correctly aligned partition, and should this be a
0xda partiton (& then I use metatdata 1.2 for mdadm)?
*Chunk size:
After reading MANY different opinions, I'm guessing staying at the
default chunk size is optimal? Anyone want to add to this argument?
*After partitioning the 8 drives, is this the correct sequence?
mdadm --create /dev/md0 --metadata=1.2 --auto=md --chunk=64
--level=raid6 --raid devices=8 /dev/sd[abcdefgh]1
mdadm --detail --scan >> /etc/mdadm.conf
mdadm --assemble /dev/md0 /dev/sd[abcdefg]1
*After this, do I mkfs ext4 first, or LVM first?
*What stride and stripe values should I use?
If you've read this far: Wow! - big thanks.
If you're going to venture some help or affirmation - BIGGER thanks! :=)
Kind regards to all,
Zoltan
This is where I am, but I'd like to get it right, so am happy to delete
& restart, if the current state is not fixable.:
**************************************************
root@gs0:/home/geograph# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md_d0 : active raid6 sde1[4] sdg1[6] sdh1[7] sdc1[2] sda1[0] sdb1[1]
sdd1[3] sdf1[5]
11721071616 blocks level 6, 64k chunk, algorithm 2 [8/8] [UUUUUUUU]
unused devices: <none>
root@gs0:/home/geograph#
**************************************************
root@gs0:/home/geograph# mdadm -E /dev/md_d0
mdadm: No md superblock detected on /dev/md_d0.
**************************************************
root@gs0:/dev# ls -la /dev/md*
brw-rw---- 1 root disk 254, 0 2010-11-13 16:41 /dev/md_d0
lrwxrwxrwx 1 root root 7 2010-11-13 16:41 /dev/md_d0p1 -> md/d0p1
lrwxrwxrwx 1 root root 7 2010-11-13 16:41 /dev/md_d0p2 -> md/d0p2
lrwxrwxrwx 1 root root 7 2010-11-13 16:41 /dev/md_d0p3 -> md/d0p3
lrwxrwxrwx 1 root root 7 2010-11-13 16:41 /dev/md_d0p4 -> md/d0p4
/dev/md:
total 0
drwxrwx--- 2 root disk 140 2010-11-13 16:41 .
drwxr-xr-x 18 root root 4520 2010-11-14 11:42 ..
brw------- 1 root root 254, 0 2010-11-13 16:41 d0
brw------- 1 root root 254, 1 2010-11-13 16:41 d0p1
brw------- 1 root root 254, 2 2010-11-13 16:41 d0p2
brw------- 1 root root 254, 3 2010-11-13 16:41 d0p3
brw------- 1 root root 254, 4 2010-11-13 16:41 d0p4
root@gs0:/dev#
***********************************************
root@gs0:/home/geograph# fdisk -lu
WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util
fdisk doesn't support GPT. Use GNU Parted.
Disk /dev/sda: 2000.4 GB, 2000398934016 bytes
256 heads, 63 sectors/track, 242251 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sda1 63 3907024127 1953512032+ fd Linux raid
autodetect
(All 8 disks are as above)
************************************************
root@gs0:/home/geograph# parted /dev/sde
GNU Parted 2.2
Using /dev/sde
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Warning: /dev/sde contains GPT signatures, indicating that it has a GPT
table. However, it does not have a valid fake msdos partition table, as
it should. Perhaps it was
corrupted -- possibly by a program that doesn't understand GPT partition
tables. Or perhaps you deleted the GPT table, and are now using an
msdos partition table. Is this a
GPT partition table?
Yes/No? yes
Model: ATA ST32000542AS (scsi)
Disk /dev/sde: 2000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name
Flags
1 17.4kB 134MB 134MB Microsoft reserved
partition msftres
(parted)
****************************************************
--
===========================================
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° 6'16.35"S 18°28'5.62"E
Tel: +27-21-7884897 Mobile: +27-83-6004028
Fax: +27-86-6115323 www.geograph.co.za
===========================================
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