I merged your comments. Please let me know if there’s anything amiss.

-d

FreeBSD Duplex mirror using GEOM

– CD OS Install
* Partition : Commit entire disk (ad4)
* Partition : / 512M
SWAP 2GB
/var 2GB
/tmp 512M
/usr remainder
* Set up duplex mirror using GEOM (before CD reboot)
– INSTALL
– ALT-F4
– # csh
– # sysctl kern.geom.debugflags=16
result : kern.geom.debugflags: 0 -> 16
– # gmirror label -v -b round-robin gm0 /dev/ad4
result : Metadata value stored on /dev/ad4
– # echo geom_mirror_load=”YES” > /boot/loader.conf
– # cp /etc/fstab /etc/fstab.orig
– # vi /etc/fstab (replace /dev/ad4 with /dev/mirror/gm0)
– reboot
– # vi /etc/rc.conf
# need to do this to make dumping cores happy since it won’t use a gmirror’ed drive
dumpdev=”NO”

– SYNC
– # swapinfo
– # gmirror insert gm0 /dev/ad6
result : GEOM_MIRROR: Device gm0: provider ad6 detected.
result : GEOM_MIRROR: Device gm0: rebuilding provider ad6.
– # gmirror list | more
– # gmirror status

– FAILURE RECOVERY
– REMOVE A LIVE DISK FROM A MIRROR (but keep in machine)
– # gmirror deactivate gm0
– # gmirror forget gm0
(forget about removed devices)
– # gmirror status

– BRING A NEW DISK ONLINE
- ***insert drive***
- # atacontrol detach ***ata-channel-to_remove ex : ata3 for /dev/ad6***
(make sure channel is not initialized)
- # atacontrol attach ***ata-channel-to_remove ex : ata3 for /dev/ad6***
- # gmirror forget gm0
- # gmirror insert gm0
- # gmirror status

- HOT UNPLUG A LIVE DISK FROM A MIRROR !!!BROKEN IN 6.0
- # gmirror deactivate gm0 ***disk-to-remove devname ex : ad6***
- # gmirror forget gm0
(forget about removed devices)
- # atacontrol detach ***ata-channel-to_remove ex : ata3 for /dev/ad6***
- ***remove drive***
- # atacontrol list

computer1# fdisk /dev/ad0
******* Working on device /dev/ad0 *******
parameters extracted from in-core disklabel are:
cylinders=77545 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won’t work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=77545 heads=16 sectors/track=63 (1008 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
start 63, size 78156162 (38162 Meg), flag 80 (active)
beg: cyl 0/ head 1/ sector 1;
end: cyl 1023/ head 254/ sector 63
The data for partition 2 is:

The data for partition 3 is:

The data for partition 4 is:

bhw-proxy.hons.com.np# fdisk -s /dev/ad2
fdisk: invalid fdisk partition table found
fdisk: read_s0: Unknown error: 0
computer1# fdisk /dev/ad2
******* Working on device /dev/ad2 *******
parameters extracted from in-core disklabel are:
cylinders=77542 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won’t work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=77542 heads=16 sectors/track=63 (1008 blks/cyl)

fdisk: invalid fdisk partition table found
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
start 63, size 78162273 (38165 Meg), flag 80 (active)
beg: cyl 0/ head 1/ sector 1;
end: cyl 741/ head 15/ sector 63
The data for partition 2 is:

The data for partition 3 is:

The data for partition 4 is:

Any suggestions? Please

As as workaround I installed a minimal freebsd system on a temporarily third disk, boot from it and created the raid. Then take it out again.

http://www.nabble.com/misc-120169:-gmirror-commands-error-with-“Class-not-found”-or-other-td15190746.html

I have a computer with one hard disk (single slice ad0s1) running with FreeBSD. This computer is used as a WEB server, mail server, DNS server, … For a best security, I would like to establish a RAID-1 for the system partitions using your “howto” with a second new hard drive (mirror). My question is :

Is it possible to establish a RAID-1 on my system using your “howto” and keeping all my first drive data (WEB server, mail server,…) ? In fact, I really need a mirror to upgrade my security, but I don’t want to loose my data on my first hard drive.

Thanks for your tutorial.

Best regards.

F. Langlet-Cauet.

I’ve been running a server using FreeBSD 5.3 and gmirror to mirror two identical IDE hard drives. This howto was very helpful when setting up. Its been running great for over a year. But recently everything went down and when I reboot and put a monitor on it I get the following errors on screen:

GEOM_MIRROR: Device gm0: provider ad1 disconnected
GEOM_MIRROR: Device gm0: provider mirror/gm0 destroyed
GEOM_MIRROR: Device gm0: rebuilding provider ad0 stopped

Fatal trap 12: page fault while in kernel mode… (this is followed by details about the fault)

These errors are preceded by other related error information that flys by on the screen and I have no way of seeing them again.

Does anyone now what steps I should take to figure what is going on and try to recover data or get the machine to boot?

Thanks so much,
S.

# gmirror list
Geom name: gm4
State: COMPLETE
Components: 1
Balance: round-robin
Slice: 4096
Flags: NONE
GenID: 0
SyncID: 1
ID: 3556157093
Providers:
1. Name: mirror/gm4
Mediasize: 250059349504 (233G)
Sectorsize: 512
Mode: r4w4e5
Consumers:
1. Name: ad4
Mediasize: 250059350016 (233G)
Sectorsize: 512
Mode: r1w1e1
State: ACTIVE
Priority: 0
Flags: NONE
GenID: 0
SyncID: 1
ID: 3808931721

The difference ist exactly 512 bytes. Is this the last sector, where geom stores the meta data?

Is the difference with the geometry critical?

I have a mirror with two identically SATA drives. The mirror was build, as the system was installed a year ago.

This are the gemoetry for ad4/ad6: cylinders=484521 heads=16 sectors/track=63 (1008 blks/cyl)

And this is the geometry for gm4: cylinders=30401 heads=255 sectors/track=63 (16065 blks/cyl)

The one partition has this size (is for ad4/ad6 and gm4):

The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
start 63, size 488397042 (238475 Meg), flag 80 (active)
beg: cyl 0/ head 1/ sector 1;
end: cyl 168/ head 14/ sector 63

You can see, that the partition is bigger than the gm4 geometry.

Any idea, what I can do? A fdisk -u mirror/gm4 will not work, because fdisk prins:

fdisk: Geom not found
fdisk: Failed to write sector zero

mounting root from ufs:/dev/mirror/gm0s1a
setrootbyname failed
ffs_mountroot: can’t find rootvp

How can I fix this prob to boot FreeBSD.

I’d ask around on -hackers but I’m pretty sure bad block mapping is done mostly within the drives these days: they present a series of blocks to the OS that is smaller than their absolute physical capacity, and internally map around any bad blocks as they are encountered. An OS may in turn encounter bad blocks, and does a similar thing. If I were implementing GEOM and gmirror, that easiest thing to do is that if you have to remap a bad block on one drive, you re-map it in the virtual drive. So, if someone slips you a replacement drive with many bad blocks, you just map those into the virtual drive. Maybe if you drop drives, you can free up those bad blocks from the OS’ list.

I think it is good to think about these things, but I’d suggest a bit more research before you start making your life more inconvenient to solve troubles that have hopefully been addressed already. :)

Cheers,
-danny

I can’t say that I agree with you on this one. From a user perspective typing ‘load’ or ‘prefer’ are both easier to use than ’round-robin’; fewer characters ;-) But seriously, in my desktop machine I have a duplexed gmirror built off of 2 disks that have the same geometry but one is udma66 and the other is udma100, I’m pretty sure using ‘load’ is better in this situation and probably others too.

Regardless, the how-to is still a wonderful thing. I certainly don’t want to take anything away from it. However, a little constructive criticism can be a good thing, so….

If I may suggest, although the how-to tells you how to set-up the mirror, it never mentions what to do when an actual disaster happens (i.e. when a disk needs to be changed).

Some things to consider:

1. Most modern disks will not be the same size even if “you have a pair of identical IDE … drives”. This is because the integrated drive electronics account for imperfections in the media (bad tracks/sectors). Thus the command “gmirror label -v -b round-robin gm0 /dev/ad4″ in step 4 should *i think* be more like “gmirror label -v -b round-robin gm0 /dev/ad6 /dev/ad4″. This will create a mirror only as big as the smallest drive. If you don’t do this, you just might see a message that says you can’t insert ad6 because it’s too small (even though the disks are ‘identical’). In addition, to quote the gmirror manpage: “The order of components is important, because a component’s priority is based on its position (starting from 0). The component with the biggest priority is used by the prefer balance algorithm and is also used as a master component when resynchronization is needed, e.g. after a power failure when the device was open for writing.” In light of this, I’m not sure if the command should be “gmirror label -v -b round-robin gm0 /dev/ad6 /dev/ad4″ or “gmirror label -v -b round-robin gm0 /dev/ad4 /dev/ad6″ – but one may be better than the other. I mean… the gmirror manpage does say order is important, right?

2. When installing the system (in step 1) it might not be a bad idea to create a slice that is actually smaller (by say 32-128mb) than the drive allows – or to install the system to the truly smallest drive. This will insure that when/if a drive needs to be replaced you can simply use the same make and model (or a drive with the same physical geometry) and not worry about size discrepencies.

3. Replacing a drive can be simple if you have a new one on hand. If it isn’t the boot drive that has failed (or the mirror is already running and you have hot-swap hardware) then it’s just a matter of ‘gmirror forgeting/removing’ the old disk and ‘gmirror inserting’ the new disk. If you have hot-swappable hardware you shouldn’t even have to reboot. If the boot drive failed (and you can’t [re]boot) you’ll need the fix-it cd as you recommend to ‘forget/remove’ the drive, and ‘insert’ another. Use ‘gmirror status’ to wait until the mirror rebuilds itself before exiting fixit (since it was the boot drive that failed). Booting a partially rebuilt disk simply can’t be a good idea imho.

4. The crib sheet assumes you have a pair of identical IDE disk drives, which is a good thing. Assuming otherwise would introduce too much complexity for a simple how-to. However, this just makes the previous three considerations that much more important. After all, what good is having a mirror if you can’t rebuild it after a failure?

Now, as you can probably tell, I’m not 100% sure about a lot of this. And I may not have written it out completely or perfectly clear. But hopefully these suggestions can make a good how-to even better!

But how about remote administrator? That doesn’t have acces to server hardware, only network connection with SSH access?