Can you put /boot into software RAID during installation?

wardhj · #1 12th October 2011, 03:30 AM

During the power-on sequence (before the OS starts), there is a screen called "Intel Matrix Storage Manager". It is set to RAID1. Everything on the screen looks good except the status is a yellow "Initialize" instead of a green "Normal". Intel support told me that I need a special driver, and they don't support Linux. What should I do?

***Dangermouse*** · #2 12th October 2011, 07:29 AM

Welcome to the forum,
to be honest i wouldnt bother, hardware raid is pretty slow, compared to software raid

wardhj · #3 12th October 2011, 02:07 PM

Dangermouse, thanks for the intel. Can I set up software RAID1 _after_ Fedora installation, with all files from the installation (including GRUB and boot sector) on the RAID? I don't see how this is possible unless setting up the RAID is the first step in the installation.

***Dangermouse*** · #4 12th October 2011, 03:27 PM

what i did was a 500mb raid partion on each drive and set them to raid1(boot), then raid partion with all space left on all drives on raid 0(/), i didnt do swap as i had over 2gig mem, this i found to the fastest for me, however if a drive fails then the sytem wont boot
(not that it happened to me), with that set up you should get the fastest speed, but its not considered a safe way for breakdowns etc..
Others may have different opinions

Edit Swap can be raid 1 or raid 0 if used.

wardhj · #5 21st October 2011, 07:17 PM

During installation, Anaconda asks me which of my two disks should have the "boot loader".

Now I'm confused. I want software RAID1. If the boot loader is on only one of the two disks, then I won't have full RAID1.

***bob*** · #6 21st October 2011, 07:26 PM

Does this help? http://docs.fedoraproject.org/en-US/...ng-raid-hw-x86

wardhj · #7 21st October 2011, 07:30 PM

Thanks Bob. Yes, that is the correct documentation. I already had it up in my browser.

My problem was due to my error. I clicked "Use All Space" instead of the "Create Custom Layout" option which is required to set up software RAID for installation.

wardhj · #8 21st October 2011, 07:58 PM

Can you put /boot into software RAID1 during installation?

In other words, is is possible, during Fedora 15 installation, to put all the files necessary for booting into software RAID1?

If not, what is the use of software RAID1? If you can't boot, nothing else matters.

jpollard · #9 21st October 2011, 08:48 PM

Nope... well, not usually.

The problem with all software raid configurations and booting is that the configuration has to be loaded before the system can be loaded. That would require grub to be able to scan for raid configurations, build the raid, and THEN it could read the kernel into memory.

Now with a simple raid 1, it may be possible by treating the boot disk as a single unit during boot, and only becoming a member of the raid after the system is up.

The problem with this is that if the boot disk is removed, then the mirror, must become the boot disk... And that depends on both disks being on the same controller... Even then, it doesn't necessarily work because the actual boot blocks are specific to the disk.

For raid volumes, the volume header is not the same as a partition header... and each member of a raid group is uniquely identified so that the raid can be identified by the system. In addition, the partition definitions on PCs are not large enough to hold raid information - so the raid volumes are more like an extended partition - the partition table only defines the low level physical partition, then a logical volume header is added within the partition... and within the logical volume partition (which spans one or more partitions) is divided up into more partitions... which then hold the filesystem information.

What I used to do for uptime operations was to maintain two boot partitions (limited size). When updates come in they get applied to the current active boot partition. After it is validated, I would copy it to the alternate boot partition and if necessary, re-create the boot blocks on that drive.

Putting a /boot partition into a raid is not really that useful - it is only updated when new kernels are put out. Keeping a bootable backup (on another drive of course) is not that hard.

It used to be possible to use dd to make that copy. Now that disks are no longer identified by hardware, that fails - you get two identical partitions/drives, with identical identifications (UUID, volume name,...) and that makes usage difficult. Possible, but once the boot disk is duplicated, it has to be removed from the system and put on a shelf.

jenaniston · #10 21st October 2011, 08:58 PM

Quote:

Originally Posted by jpollard

. . .Putting a /boot partition into a raid is not really that useful -

Check this page's section "Booting from RAIDs" and the /boot partition ... it may be helpful to ya' ?

http://docs.fedoraproject.org/en-US/...setup-x86.html

Good luck.

jpollard · #11 21st October 2011, 09:13 PM

No help there at all. It just mentions hardware raid.

All it has is:

Quote:

f you have a RAID card, be aware that some BIOSes do not support booting from the RAID card. In cases such as these, the /boot/ partition must be created on a partition outside of the RAID array, such as on a separate hard drive. An internal hard drive is necessary to use for partition creation with problematic RAID cards.
A /boot/ partition is also necessary for software RAID setups.
If you have chosen to automatically partition your system, you should select Review and manually edit your /boot/ partition.

But nothing about using a raid1.

wardhj · #12 21st October 2011, 10:11 PM

jpollard: Your reply looks like the straight dope. I could not absorb it in a single reading, but I'll keep trying. Thanks.

jeaniston: I think jpollard is right, your link does not directly address my question. And I had already found those installation instructions. But thanks anyhow.

scott32746 · #13 21st October 2011, 10:28 PM

Hello,

I have always ran my fedora /boot in a raid ( mirror ) config.

/dev/md0 1007884 114704 841984 12% /boot

md0 : active raid1 sda1[0] sdc1[1]
1023988 blocks super 1.0 [2/2] [UU]

One thing you can do is set of grub commands on the second disk to make it boot up if you lose your first drive.

wardhj · #14 21st October 2011, 11:04 PM

jpollard: Well, I am still confused. Suppose a user had

/dev/sda1 /boot
/dev/sda2 RAID

/dev/sdb RAID

and /dev/sda fails. Now he needs to replace /dev/sda. He does a shutdown and physically installs a new drive in the /dev/sda slot. Now he can't boot because the machine contains no /boot.

And even if he hot-replaces /dev/sda (without a shutdown), rebuilding will not restore /boot. So he can not restart the machine.

In other words, the limitation you have described appears to imply that software RAID is useless for 50% of disk failures (ie, when the boot disk is the one that fails).[COLOR="Silver"][COLOR="Silver"][COLOR="Silver"][COLOR="Silver"]

---------- Post added at 05:04 PM ---------- Previous post was at 05:03 PM ----------

Quote:

Originally Posted by scott32746

Hello,

I have always ran my fedora /boot in a raid ( mirror ) config.

/dev/md0 1007884 114704 841984 12% /boot

md0 : active raid1 sda1[0] sdc1[1]
1023988 blocks super 1.0 [2/2] [UU]

One thing you can do is set of grub commands on the second disk to make it boot up if you lose your first drive.

scott32746: How do you put /boot into the RAID1 mirror? Do you use a "fake RAID" setup, where the hardware is RAID-aware? Or do you use the normal Fedora installation procedure?

For me, the normal Fedora installation does not allow putting /boot into the RAID, because it requires that the /boot partition and the two RAID partitions be created all in one step.

jpollard · #15 22nd October 2011, 03:33 AM

Umm... you cant use

Quote:

/dev/sda1 /boot
/dev/sda2 RAID

/dev/sdb RAID

for a raid (disk size of sdb will be different from sda2).

The partitioning of sdb must match that of sda. Then you can raid sda2 and sdb2.

If you have sda1 as /boot, you can then COPY it to sdb1.

The problem with raiding sda1 and sdb1 is still the problem of nested partitions. There can only be one boot disk. If you remove that boot disk (due to failure, or even replacement) the system will not boot until you reinstall the boot blocks.

RAID 1 (mirroring) will not do that because the boot block (at least as far as the MBR) is not part of the filesystem. Nor is it part of the LVM for software raid. And rebuilding a mirror will not rebuild the MBR on a disk.

It MAY rebuild a partition boot block in an LVM, but that isn't the same block as the MBR.