Hi,
One last quick question:
Neil Brown <neilb@xxxxxxx> 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 an 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 array is
entirely in sync you can
echo repair> /sys/block/md0/md/sync_action
and wait a while.
****************************************************
I have compiled the following mdadm on my Ubuntu 64 bit 10.04 Desktop
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
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 = 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
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
have offered, I have just run:
mdadm --create /dev/md0 --metadata=1.2 --auto=md --assume-clean
--bitmap=internal --bitmap-chunk=131072 --chunk=512 --level=6
--raid-devices=8 /dev/sd[abcdefgh]
It took a nano-second to complete!
The man-pages for assume-clean say that "the array pre-existed". Surely
as I have erased the HDs, and now have no partitions on them, this is
not true?
Do I need to re-run the above mdadm command, or is it safe to proceed
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]
[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
[8/8] [UUUUUUUU]
bitmap: 0/8 pages [0KB], 131072KB chunk
unused devices: <none>
*******************************************************
--
===========================================
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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