* partitionable md partition size caps at 0.4TB
@ 2008-11-13 12:00 Jan Wagner
2008-11-13 13:12 ` Michal Soltys
0 siblings, 1 reply; 3+ messages in thread
From: Jan Wagner @ 2008-11-13 12:00 UTC (permalink / raw)
To: linux-raid
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?
Further infos below.
root@abidal:~# uname -a
Linux abidal 2.6.27-7-generic #1 SMP Tue Nov 4 19:33:06 UTC 2008 x86_64 GNU/Linux
root@abidal:~# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.10
DISTRIB_CODENAME=intrepid
DISTRIB_DESCRIPTION="Ubuntu 8.10"
root@abidal:~# cat /proc/partitions|grep md
254 0 9035047936 md_d0
254 1 15622 md_d0p1
254 2 445097720 md_d0p2
root@abidal:~# sfdisk /dev/md_d0
Checking that no-one is using this disk right now ...
OK
Disk /dev/md_d0: 2258761984 cylinders, 2 heads, 4 sectors/track
Old situation:
Units = cylinders of 4096 bytes, blocks of 1024 bytes, counting from 0
Device Boot Start End #cyls #blocks Id System
/dev/md_d0p1 0+ 3905 3906- 15622 83 Linux
/dev/md_d0p2 3906 111278335 111274430 445097720 83 Linux
/dev/md_d0p3 0 - 0 0 0 Empty
/dev/md_d0p4 0 - 0 0 0 Empty
root@abidal:~# mdadm -D /dev/md0
mdadm: md device /dev/md0 does not appear to be active.
root@abidal:~# mdadm -D /dev/md_d0
/dev/md_d0:
Version : 00.90
Creation Time : Thu Nov 13 11:58:59 2008
Raid Level : raid0
Array Size : 9035047936 (8616.49 GiB 9251.89 GB)
Raid Devices : 12
Total Devices : 12
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Thu Nov 13 11:58:59 2008
State : clean
Active Devices : 12
Working Devices : 12
Failed Devices : 0
Spare Devices : 0
Chunk Size : 1024K
UUID : f1945a73:83d2bea9:b96e9208:11a3b9ec (local to host
abidal)
Events : 0.1
Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
3 8 65 3 active sync /dev/sde1
4 8 81 4 active sync /dev/sdf1
5 8 97 5 active sync /dev/sdg1
6 8 113 6 active sync /dev/sdh1
7 8 129 7 active sync /dev/sdi1
8 8 145 8 active sync /dev/sdj1
9 8 161 9 active sync /dev/sdk1
10 8 177 10 active sync /dev/sdl1
11 8 193 11 active sync /dev/sdm1
thanks,
- Jan
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: partitionable md partition size caps at 0.4TB
2008-11-13 12:00 partitionable md partition size caps at 0.4TB Jan Wagner
@ 2008-11-13 13:12 ` Michal Soltys
2008-11-14 8:23 ` Jan Wagner
0 siblings, 1 reply; 3+ messages in thread
From: Michal Soltys @ 2008-11-13 13:12 UTC (permalink / raw)
To: Jan Wagner; +Cc: linux-raid
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
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: partitionable md partition size caps at 0.4TB
2008-11-13 13:12 ` Michal Soltys
@ 2008-11-14 8:23 ` Jan Wagner
0 siblings, 0 replies; 3+ messages in thread
From: Jan Wagner @ 2008-11-14 8:23 UTC (permalink / raw)
To: Michal Soltys; +Cc: linux-raid
Hello Michal,
On Thu, 13 Nov 2008, Michal Soltys wrote:
>> 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.
>
> 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).
Aha, with GPT it works perfectly,
parted /dev/md_d0 --script mklabel gpt
parted /dev/md_d0 --script mkpart primary1 0 128M
yes | parted /dev/md_d0 -- mkpart primary2 128M -1
... mkfs.* ...
parted /dev/md_d0 --script print
Number Start End Size File system Name Flags
1 17.4kB 128MB 128MB ext2 primary1
2 128MB 9252GB 9252GB xfs primary2
and the final size of md_d0p2 is a correct 9252GB. The system does not
boot from RAID, we just use the raid0 for >>4 Gbps data acquisition. Good
to know about the newer superblock versions (mdadm -e option).
Thanks for your help!
- Jan
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-11-13 12:00 partitionable md partition size caps at 0.4TB Jan Wagner
2008-11-13 13:12 ` Michal Soltys
2008-11-14 8:23 ` Jan Wagner
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