Jan Wagner wrote:
Hello,
is it possible to create md partitions larger than 0.4TB?
We have >=9TB RAID-0 systems, and I tried to create a partitionable
two-partition md with mdadm --auto=mdp2 and partition it into for
example 16MB and ~9TB. For partitioning /dev/md_d0 I have tried sfdisk,
fdisk, cfdisk, parted, ... Regardless of the partitioning tool, the ~9TB
partition always ends up as 455780.07MB i.e. 0.4TB.
There is no problem to create a large 9TB single partition on a
non-partitionable /dev/md0. Is the 445097720 blocks (0.4TB) "cropping" a
bug or a real limitation with mdp partitionable raid?
I'm assuming you tried standard MBR layout - you can't go above ~ 2TB
limit with it - you need either GPT, or use the device directly (as in
md0 case). I have one 1.5TB partition running happily on one of my
systems (still within limits of old MBR layout, but under GPT).
The old md superblock format you used has no such limitation (there're
others though - maximum 28 components, and 2TB/component). It's really
better to use one of the 1.x superblocks - check out mdadm's -e option.
If you plan to boot up from a GPT partition on a "legacy" system, you
will need either syslinux/extlinux or patched grub (and possibly others
- such as grub2). Not your case as far as I can see, but keep that in
mind just in case.
- do you have any problems with creating a partition with size of let's
say 1.8TB and within the first 2TB ?
- check if parted have any problems with creating GPT layout using sizes
you require (and make sure your kernel is compiled with GPT support).
For a reference, one of my systems:
13:32 > mdadm -D /dev/md/d0p2
/dev/md/d0p2:
Version : 01.00.03
Creation Time : Sat Jul 28 12:44:34 2007
Raid Level : raid5
Array Size : 1438617600 (1371.97 GiB 1473.14 GB)
Used Dev Size : 976060928 (465.42 GiB 499.74 GB)
Raid Devices : 4
Total Devices : 5
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Thu Nov 13 13:32:41 2008
State : clean
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
Name : d0
UUID : acf9b8b0:95ba6218:bc4f9bff:67a1fe93
Events : 2814
Number Major Minor RaidDevice State
0 8 3 0 active sync /dev/sda3
1 8 19 1 active sync /dev/sdb3
2 8 35 2 active sync /dev/sdc3
4 8 51 3 active sync /dev/sdd3
5 8 67 - spare /dev/sde3
13:53 > parted /dev/md/d0
GNU Parted 1.8.8
Using /dev/md/d0
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Model: Unknown (unknown)
Disk /dev/md/d0: 1499GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
1 17.4kB 25.8GB 25.8GB
2 25.9GB 1499GB 1473GB xfs
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