Rumor is it is not possible to boot an operating system from the software array. Not exactly.
All of the modern boot loaders, ones coming from NT, Linux LILO, and GRUB, would happily boot from a RAID 1 (mirror).
It should be noted that some additional measures should be done to achieve boot redundancy if you are going to build a RAID. Since the mirroring does not cover the Master Boot Record, you should copy the MBR sector manually between hard disks in software mirror. If you omit the above, then
when the primary (boot) drive dies, you are left with an unbootable system.
Surely there will be no irreversible loss of data - all you need is to just attach the good hard drive into a working PC and read it, but no automatic recovery is possible if the drive stops working in operation, requiring a reboot.
Wednesday, June 13, 2012
Monday, January 30, 2012
Make a software RAID bootable?
Is it possible to create a bootable software RAID0, RAID 5, or JBOD?
The answer is "no". It is impossible to start an operating system off a software RAID0, RAID 5, or JBOD.
A hardware controller is required to be able to to make a RAID bootable. You cannot start an operating system from the software RAID because the RAID is not readable until the operating system is done loading, and the operating system itself is on the RAID.
Your only option is to start an operating system using a software RAID 1. To boot from a "second" drive of a software RAID1, one may need to copy the master boot record first, because typically the master boot record would not be subjected to mirroring.
The answer is "no". It is impossible to start an operating system off a software RAID0, RAID 5, or JBOD.
A hardware controller is required to be able to to make a RAID bootable. You cannot start an operating system from the software RAID because the RAID is not readable until the operating system is done loading, and the operating system itself is on the RAID.
Your only option is to start an operating system using a software RAID 1. To boot from a "second" drive of a software RAID1, one may need to copy the master boot record first, because typically the master boot record would not be subjected to mirroring.
Tuesday, January 10, 2012
Complex level RAID100
If you open Wikipedia you find out that RAID100 is considered as nested RAID level. It is said that RAID 100 is a RAID0 built from RAID10 arrays. Thus it turns out that on-disk contents of RAID 100 will be exactly the same as in RAID 10.
So, it is possible to obtain RAID 0 from RAID 100 by removing one of the disks of each mirror set. From the RAID recovery point of view, RAID100 recovery just boils down to RAID0 recovery given that you are able to fetch a full set of RAID0 disks.
So, it is possible to obtain RAID 0 from RAID 100 by removing one of the disks of each mirror set. From the RAID recovery point of view, RAID100 recovery just boils down to RAID0 recovery given that you are able to fetch a full set of RAID0 disks.
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