On 9/11/2014 6:06 AM, Greg Freemyer wrote:
If you want RAID0 or RAID1, my experience with BIOS raid for those 2 types is that is more versatile, reliable and software transparent. Since you want RAID1, assuming you are talking SATA or SAS, both disks can be written-to at the same time by the controller and it will look like a single disk to windows and linux (and any other OS). You and I have had different experiences. The most obvious is your statement about Linux seeing a fakeraid as a single disk. With the fakeraid I've attempted to use, Linux sees each disk and has to be made to recognize the fakeraid exists and read the raid config out of
I disagree, *depending* on what type of RAID you want. the bios, then take the responsibility of managing the disks just as it does with software raid.
Fyi: fake raid works by implementing custom firmware in the bios I/o interface used during boot. Thus Windows and Linux only see a single drive during the boot process, but for Linux as soon as the normal ATA/scsi drivers kick in the bios is bypassed and the kernel has to manage the raid array itself. dmraid (as opposed to MD raid or mdraid) is the Linux package that is responsible for reading the config out of the bios and setting up the Linux kernel to manage the disks correctly.
My experience has been identical to Greg's, and Software Raid has been bullet proof. There is one area that you have to be aware of if you put /boot on a mirrored (raid1) drive, the system will always boot from which ever disk your menu.lst says to boot from even if that is part of a MD raid. If that disk fails you have to manually switch your menu.lst to the other. (This is why I avoid /boot on MD raid.) I've had several fake raid cards and several fake raid mother boards, and each time, I did around to find the jumper that disables the fake raid and just use the controllers as separate channels. (The cheapest of the cheap fake raid cards also fake using multiple channels, so buyer beware, your WRITES will be done serially, not in parallel on these cheap cards.). -- _____________________________________ ---This space for rent--- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org