Solved [Solved] graid or gmirror

H

hashime

Hello

I am unsure what the differences between graid (RAID1) and gmirror are, from a user's point of view. I read through the handbook chapters, that is all fine, but what are the advantages of one over the other? What's the "default" RAID1 implementation one should use? I understand that gmirror has troubles with GPT, but other than that? I want to use the RAID1 for / and /usr/home, in case that matters.
 
Re: graid or gmirror

graid(8) uses the on-board RAID controllers on many motherboards. Advantages are that the RAID device is present at boot, and so directly bootable. It can be whatever type of RAID offered by the motherboard RAID, not just a mirror.

gmirror(8) is a mirror. The BIOS boots from one drive and then the mirror is created after the kernel starts. Advantages are that it's not motherboard RAID.
 
Re: graid or gmirror

I have the option to do both. Is there a default option for such cases? Should I choose one over the other if both are possible?
 
Re: graid or gmirror

wblock@ said:
graid(8) uses the on-board RAID controllers on many motherboards.
Click to expand...
Besides "fake-RAID" controllers isn't it also able to use software RAID? It's been a while since I last used it.

hashime said:
I have the option to do both. Is there a default option for such cases? Should I choose one over the other if both are possible?
Click to expand...
There are no "defaults", you get to choose whatever you want ;)

But I'd steer clear of any fake-RAID solutions as they tend to be specific to mainboards and the type of controller that's used. It's usually not possible to stick the RAID array on some other controller and still be able to read the data. Which is going to pose a serious problem if the controller decides to break down.

Instead of gmirror/graid I highly recommend ZFS.
 
Re: graid or gmirror

Gmirror if I'd had to choose out of just those two. However, gmirror(8) has some limitations like not being able to mirror whole GPT-partitioned disks and if you have multiple mirrors you can't set priorities between them, this can lead to serious thrashing when all of the mirrors have to be rebuilt after a crash. ZFS avoids many of these pitfalls nicely and should be used if the hardware allows it.
 
Re: graid or gmirror

SirDice said:
wblock@ said:
graid(8) uses the on-board RAID controllers on many motherboards.
Click to expand...
Besides "fake-RAID" controllers isn't it also able use software RAID? It's been a while since I last used it.
Click to expand...

"Fake-RAID" controllers are all software RAIDs, they are just dumb SATA/IDE controllers with a special RAID BIOS that allows creation and management of the RAID arrays. A software driver is still usually needed on OS side as well.
 
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