Installing Slackware 13.37 on 3 disk md raid10 without init.rd
Hi all
I want to share my experiment with installing linux on a 3 disk md raid10. My rig: Amd phenomII X4, 3.4 GHz 4 GB DDR2 2 x 1 TB Sata HDD /dev/sda,/dev/sdb 1 x 2 TB Sata HDD /dev/sdc Why raid10: There are two types of raid hardware and software. The hardware raid you find on motherboards is more a sort of software raid. I choose for software raid with the md driver because then it is possible to use raid10 with 3 disks and/or partitions, from which you may lose one disk without losing your system and you get better read performance with big files because the data is striped across the disks so you can read from multiple spindels. With hardware raid10 you need 4 disks,which are divided in 2 pairs. From each pair you may lose 1 disk. So for more performance and more safety. Warning raid is no substitute for back-up. But there is a price. You lose half your disk space so with my setup two 1 TB disks and one 2 TB disk which I divided in two because raid10 needs equally sized disk/partitions. I get a 3 TB raid10 which gives a usable space of 1.5 TB. I used a Slackware current ISO which I put on a usb stick with unetbootin. The boot order in BIOS was set to sdc. And I used the BIOS boot menu by pressing F8 to boot the usb stick. The first thing I did was create two partitions on sdc. A small 30 MB boot partition which will not be a part of the raid10 array because lilo can not boot from a software raid10. And a second partition of 1 TB. After deleting all partitions from sda and sdb. I created the raid10 array. Code:
bash-4.1# mdadm --create /dev/md_d0 --auto=yes --level=raid10 --bitmap=internal --layout=f2 --chunk=256 --raid-devices=3 --metadata=0.90 /dev/sda /dev/sdb /dev/sdc2 Code:
fdisk /dev/md_d0 Code:
Disk /dev/md_d0: 1499.8 GB, 1499837497344 bytes Code:
root=/dev/md_d0p2 After some more reading I added as kernel parameter Code:
raid=part md=d0,/dev/sda,/dev/sdb,/dev/sdc2 root=/dev/md_d0p2 Code:
append=" raid=noautodetect md=d0,/dev/sda,/dev/sdb,/dev/sdc2" Code:
# LILO configuration file info: http://linux.die.net/man/8/mdadm https://raid.wiki.kernel.org http://spinics.net/lists/raid/maillist.html |
RAID 10 first pairs drives into RAID 1 arrays, and then stripes across the arrays. You can theoretically lose 1/2 of the drives and not lose the array if all the failed drives are each one of the drives in their 2-drive RAID 1 group. If any entire RAID 1 group fails, the entire array is lost.
While you can do seemingly do RAID 10 with three drives using your setup, if the single 2TB drive fails you lose the entire array. This is no safer than RAID 0. You would be better off setting up RAID 0+1 where you stripe the data across the two 1TB drives in a RAID 0 array, and then mirror the array onto the 2TB drive in a RAID 1 array. That way you could lose any single drive and still recover. Or do it right and use 4 drives if you want RAID 10. |
If you had read the thread you would know that only half of the 2 TB drive is used for the raid array.md raid 10 offers a option to use 3 drives and create a real raid 10 array in which you can lose one of the drives. See http://en.wikipedia.org/wiki/Non-sta...nux_MD_RAID_10
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I did read the post. Did you read mine? Using a single drive as part of a RAID 10 array removes most of the advantage of using RAID 10. Anyway...
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Yes I did and i did lose the 2 GB drive without losing the array it came up fine.
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