Hi All, I am currently needing to build a RAID 5 on ten large 1TB Disks in several different systems, that will come over time. The systems are all running exactly the same linux version and mdadm tools, as well as being exactly the same hardware, and are populated with exactly the same drives (same capacity, manufacturer model and batch). Creating a RAID 5 array on each of these devices will take approx 15Hours+, which led me to think of the following procedure/experiment to create them faster. I found a way using Doug Gilbert's great sg3utils to zero all these disks in a very efficient manner, using sgp_dd, at near drive bandwidth, and proceeded to zero all the disks fully in about 4 hours! Once done, I then created a RAID 5 on 10 disks, waited for the rebuild to complete, stopped the array using mdadm, and dumped each of the RAID's components superblocks to files. The command used for the RAID 5 creation was the following: mdadm --create -vvv --force --run --metadata=1.2 /dev/md/d0 --level=5 --size=35879936 --chunk=64 --name=0125465 -n10 --bitmap=internal --bitmap-chunk=4096 --layout=ls /dev/sde2 /dev/sdj2 /dev/sdf2 /dev/sdg2 /dev/sdb2 /dev/sdc2 /dev/sdh2 /dev/sdi2 /dev/sdd2 /dev/sda2 The create worked fine and I waited for the rebuild to be complete before stopping the array and dumping the SBs. I then proceeded to write these same superblocks to 10 new similar disks in a different system, and used the following command to assemble the array: bin/mdadm/mdadm --assemble -vvv --force /dev/md/d0 --run --name=0125465 /dev/sde2 /dev/sdj2 /dev/sdf2 /dev/sdg2 /dev/sdb2 /dev/sdc2 /dev/sdh2 /dev/sdi2 /dev/sdd2 /dev/sda2 This subsequently led to my new array to be instantly online with no rebuild required. I figured this whole procedure would work since the disks are completely zeroed, the parity information should be zero anyways on the drives. Since zeroing all these drives took me 4 hours, I would save nearly 10 hours for any subsequent array I would need to build in the future, just by zeroing their components and dd-ing the SBs onto them. Do you think this method has its flaws? Do you think the data on it should be safe? How about the bitmap, would that be safe as long as the superblock has been copied, or should I copy this over too? Thanks in advance. Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
