On 05/02/12 18:47, Gianni Giardina wrote:
Hi. The following HowTo on the CentOS Wiki:
http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1
valid for CentOS 5, has not been updated to CentOS 6, yet. I found it very useful during the glorious CentOS 5 days and now that I've successfully ported my RAID1 experience to CentOS 6, I'd like to share it with the Community.
I have a question regarding partionable RAID : why should the --metadata=0.90 be used? in my man page (centos 6.2) i have this : -e, --metadata= Declare the style of RAID metadata (superblock) to be used. The default is 1.2 for --create, and to guess for other operations. The default can be overridden by setting the metadata value for the CREATE keyword in mdadm.conf.
Options are:
0, 0.90 Use the original 0.90 format superblock. This format limits arrays to 28 component devices and limits component devices of levels 1 and greater to 2 terabytes. It is also possible for there to be confusion about whether the superblock applies to a whole device or just the last partition, if that partition starts on a 64K boundary.
1, 1.0, 1.1, 1.2 default Use the new version-1 format superblock. This has fewer restrictions. It can easily be moved between hosts with different endian-ness, and a recovery operation can be checkpointed and restarted. The different sub-versions store the superblock at different locations on the device, either at the end (for 1.0), at the start (for 1.1) or 4K from the start (for 1.2). "1" is equivalent to "1.2". "default" is equivalent to "1.2".
given the existence of 2+ tb hdd, metadata 0.9 is no go from the start ... so, why 0.9 ?
Thanks, Adrian
On Mon, May 7, 2012 at 1:24 PM, Adrian Sevcenco Adrian.Sevcenco@cern.ch wrote:
On 05/02/12 18:47, Gianni Giardina wrote:
Hi. The following HowTo on the CentOS Wiki:
http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1
valid for CentOS 5, has not been updated to CentOS 6, yet. I found it very useful during the glorious CentOS 5 days and now that I've successfully ported my RAID1 experience to CentOS 6, I'd like to share it with the Community.
I have a question regarding partionable RAID : why should the --metadata=0.90 be used? in my man page (centos 6.2) i have this : -e, --metadata= Declare the style of RAID metadata (superblock) to be used. The default is 1.2 for --create, and to guess for other operations. The default can be overridden by setting the metadata value for the CREATE keyword in mdadm.conf.
Options are:
0, 0.90 Use the original 0.90 format superblock. This format limits arrays to 28 component devices and limits component devices of levels 1 and greater to 2 terabytes. It is also possible for there to be confusion about whether the superblock applies to a whole device or just the last partition, if that partition starts on a 64K boundary.
1, 1.0, 1.1, 1.2 default Use the new version-1 format superblock. This has fewer restrictions. It can easily be moved between hosts with different endian-ness, and a recovery operation can be checkpointed and restarted. The different sub-versions store the superblock at different locations on the device, either at the end (for 1.0), at the start (for 1.1) or 4K from the start (for 1.2). "1" is equivalent to "1.2". "default" is equivalent to "1.2".
given the existence of 2+ tb hdd, metadata 0.9 is no go from the start ... so, why 0.9 ?
I always thought it was a huge advantage for software raid that the kernel would autodetect and assemble the components. Is there a way to make that happen with 1.x metadata?
On 05/07/2012 08:24 PM, Adrian Sevcenco wrote:
On 05/02/12 18:47, Gianni Giardina wrote:
Hi. The following HowTo on the CentOS Wiki:
http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1
<snip>
given the existence of 2+ tb hdd, metadata 0.9 is no go from the start ... so, why 0.9 ?
0.90 is needed so older GRUB can boot from that RAID1 partition.
-
Adrian Sevcenco -
Les Mikesell -
Ljubomir Ljubojevic