Software RAID:
Information:
- Software RAID combines two or more physical harddisks or their partitions (RAID slices) into a single logical unit. RAID's various designs involve two key design goals: increase data reliability and/or increase input/output performance.
- You can create RAID volumes and install Lion on RAID using iATKOS ML2.
- RAID levels or types for OS X:
Striped RAID (RAID-0): A RAID-0 set splits data evenly across multiple disks with no parity information for redundancy. RAID0 is normally used to increase performance for both read and write. It can also be used as a way to create a small number of large virtual disks out of a large number of small physical ones. Simply it is a way to use the disks like using the dual or more channel RAMs, so it increases the read and write performance more than a bit. RAID0 sets are advised for the main system volumes to increase the performance of the OS.
Mirrored RAID (RAID-1): A RAID-1 set creates an exact copy of a set of data on two or more disks. This is mostly for data safety and also an increase of performance for read operations is expected. The RAID array can only be as big as the smallest member of the slices. RAID1 sets are used for security and advised for data storage volumes.
Concatenated Disk set: Which is not exactly a RAID level. The slices are merely concatenated together, end to beginning, so they appear to be a single large disk. It provides no data redundancy. This may be thought of as the inverse of partitioning. Whereas partitioning takes one physical drive and creates two or many more logical volumes, concatenation uses two or more slices to create one logical volume. No increase in performance is possible and neither increased data reliability is possible.
- Boot helper partition: OS X Software RAID systems boot using boot helper partitions and so the bootloader will be installed to boot helper partition instead of the RAID slice. If one of the RAID slices of your target RAID volume is disk0s2, then its hidden boot helper partition named as "Boot OS X" is disk0s3. Do the math for the others.
- Create RAID volumes: You can easily create RAID volumes using OS X Disk Utility. Do the partitioning if you need to, click on the target disk and then click on RAID tab, choose RAID type, name it and by pressing "+" create a new RAID set. Add the target partitions or disks to RAID set by dragging them and when you are done, click to "Create" button. The added partitions or disks will be the slices of your RAID set, in a few seconds your RAID volume will be mounted and ready for installation.
- iATKOS ML2 RAID operations:
- For RAID target, ML2 installs the bootloader to the boot helper partition of the preceding disk of the RAID set, so the first disk by your bios will be the Mac OS X boot disk.
You can install any foreign bootloaders to other harddisks of your RAID set, there will be no harm for your RAID set. On my test 3x RAID0 system, second HDD has Grub bootloader and the third one has Windows bootloader, all of them are installed seperately and running fine. Grub and Chameleon can easily boot all of the 3 OS' and also windows can be manipulated to boot them.
RAID Install Steps:
1- Create RAID volume as described above
2- Select it as destination for install
3- Click Customize and select what you need
4- Click Install
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