RAID setup: Difference between revisions
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* RAID 0 is stripping: basically two drives combined into one big drive. If one drive breaks, all data is lost so this is risky. | * RAID 0 is stripping: basically two drives combined into one big drive. If one drive breaks, all data is lost so this is risky. | ||
** With software RAID 0, you cannot have /boot on the stripped partition (at least not with GRUB 0.97). You need a separate /boot partition that is not on the RAID 0 array. | |||
** RAID 0 needs to have all partitions of different drives of the same size. This basically means that if you have 2x100GB drive, and you create a 1GB partition on the first drive, the maximum RAID 0 size combining the two disks will be 2x99GB, not 99GB+100GB. | |||
* RAID 1 is mirroring. There is redundancy but at a high cost. | * RAID 1 is mirroring. There is redundancy but at a high cost. | ||
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mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1 | mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1 | ||
When creating the array mdadm can complain about the previous presence of a filesystem. You can use mkswap to remove the filesystem (later you will probably reformat the RAID array, so that's safe). | When creating the array mdadm can complain about the previous presence of a filesystem. You can use mkswap to remove the filesystem (later you will probably reformat the RAID array, so that's safe). It can also tell you to use --metadata=0.90 format. Indeed if you use GRUB legacy, and a setup without initrd, you cannot use RAID 1 with a metadata format higher than 0.90. | ||
* To deactivate a RAID array: | * To deactivate a RAID array: | ||
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mdadm --detail /dev/md1 | mdadm --detail /dev/md1 | ||
== Rocky Linux Installer == | |||
* The Rocky Linux graphical installer supports creating RAID arrays (and more generally, a totally custom partitioning of hard drives). Its interface is not very intuitive though compared to fdisk/gparted. | |||
= LVM2 = | = LVM2 = | ||
* LVM is a set of userspace tools that allows dynamic resizing of partitions without rebooting and other stuff like that. Untested yet. | * LVM is a set of userspace tools that allows dynamic resizing of partitions without rebooting and other stuff like that. Untested yet. | ||
Latest revision as of 08:23, 6 March 2024
Concepts
Types
- A RAID setup can either be hardware (hardware card that includes a RAID controller, in this case no drivers are needed) or software (in this case Linux drivers are needed). There is a third type called firmware RAID that is neither software nor hardware. It seems no drivers are needed but there is a burden on the host CPU.
Possible setups
- RAID 0 is stripping: basically two drives combined into one big drive. If one drive breaks, all data is lost so this is risky.
- With software RAID 0, you cannot have /boot on the stripped partition (at least not with GRUB 0.97). You need a separate /boot partition that is not on the RAID 0 array.
- RAID 0 needs to have all partitions of different drives of the same size. This basically means that if you have 2x100GB drive, and you create a 1GB partition on the first drive, the maximum RAID 0 size combining the two disks will be 2x99GB, not 99GB+100GB.
- RAID 1 is mirroring. There is redundancy but at a high cost.
Tools
- mdadm is used to create the RAID arrays:
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
When creating the array mdadm can complain about the previous presence of a filesystem. You can use mkswap to remove the filesystem (later you will probably reformat the RAID array, so that's safe). It can also tell you to use --metadata=0.90 format. Indeed if you use GRUB legacy, and a setup without initrd, you cannot use RAID 1 with a metadata format higher than 0.90.
- To deactivate a RAID array:
mdadm --stop /dev/md1
- To deassociate the partitions from a RAID array:
mdadm --zero-superblock /dev/sda1 mdadm --zero-superblock /dev/sdb1
- To obtain the status of an array:
mdadm --detail /dev/md1
Rocky Linux Installer
- The Rocky Linux graphical installer supports creating RAID arrays (and more generally, a totally custom partitioning of hard drives). Its interface is not very intuitive though compared to fdisk/gparted.
LVM2
- LVM is a set of userspace tools that allows dynamic resizing of partitions without rebooting and other stuff like that. Untested yet.