Otto gave you a good answer here, but I had already provided lots of
detail, so I'm sending anyway. :)
On 06/01/2012 01:04 PM, Scott McEachern wrote:
Hello everyone,
I'm hoping that I'm missing something simple (like usual) and maybe
someone could straighten me out.
I'm trying to add a pair of 3TB drives to my workstation, which I plan
on turning into a ~3TB RAID 1 array, and seem to be having difficulty
realizing the full size of the drives.
The hardware is about a year old, and less than two years old according
to the BIOS date:
bios0: vendor American Megatrends Inc. version "2103" date 06/18/2010
bios0: ASUSTeK Computer INC. M4A785TD-V EVO
(Correction, I've since updated the BIOS to the latest version, just in
case, and it reads like so:
bios0: vendor American Megatrends Inc. version "2105" date 07/23/2010
and it makes no difference.)
(The full dmesg is below, but for now I'll just post the relevant bits.)
The BIOS happily reports the two drives as present and of 3.0TB
capacity. OpenBSD seems to recognize this as well:
sd0 at scsibus0 targ 0 lun 0: <ATA, WDC WD5000AAKS-0, 05.0> SCSI3
0/direct fixed naa.50014ee001cbd923
sd0: 476940MB, 512 bytes/sector, 976773168 sectors
sd1 at scsibus0 targ 1 lun 0: <ATA, ST3000DM001-9YN1, CC4B> SCSI3
0/direct fixed naa.5000c5004a6e56f1
sd1: 2861588MB, 512 bytes/sector, 5860533168 sectors
sd2 at scsibus0 targ 2 lun 0: <ATA, ST3000DM001-9YN1, CC4B> SCSI3
0/direct fixed naa.5000c5004a5baa2e
sd2: 2861588MB, 512 bytes/sector, 5860533168 sectors
Life is good.
...
I just wanted to get on with my day and not have any fuss, so I issued
an "fdisk -iy sd1" command on the way to disklabel'ing things. I suspect
that's my error, because fdisk says this: (I've added some commas to
make for easier reading.)
# fdisk sd1
Disk: sd1 geometry: 364801/255/63 [1,565,565,872 Sectors]
Offset: 0 Signature: 0xAA55
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
-------------------------------------------------------------------------------
0: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
1: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
2: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
*3: A6 0 1 2 - 97451 165 59 [ 64: 1,565,560,705 ] OpenBSD
Uhm, that doesn't seem right
well. it's annoying, but "rightish". :)
fdisk edits MBRs, MBR has a limit of 2TB on its structures.
So...it looks like fdisk basically did a 3TB modulo 2TB. I really
should save myself looking like a fool and check my math, but if I'm
wrong, it will teach you not to take what I say as gospel :)
Some OSs want you to switch to a new way of handling big disks, but I do
think OpenBSD will do what you want "natively".
..
A drive with half the capacity seems to have double the numbers, but not
for geometry. I suspect that fdisk is lying to me, but I could be wrong.
you are right.
Let's see what disklabel(8) has to say. On the 1.5TB drive, it looks
mostly like this (I've snipped some irrelevant partition data and added
commas to make big numbers easier to read):
..
total sectors: 2,930,277,168
boundstart: 64
boundend: 2930272065
drivedata: 0
16 partitions: (snipped)
# size offset fstype [fsize bsize cpg]
c: 2,930,277,168 0 unused
On the new 3TB drive, it looks like this:
# disklabel sd1
..
total sectors: 5,860,533,168
boundstart: 64
boundend: 1565560769
drivedata: 0
16 partitions:
# size offset fstype [fsize bsize cpg]
c: 5,860,533,168 0 unused
Wait a minute here... disklabel seems to have correct data (ignoring the
duid). I'll bet I'm failing at grade four math, but that looks roughly
like a 3TB drive.
yes, it's a 3TB disk, but at the moment, disklabel is restricting you to
just the fdisk-marked part of the drive...which is as it should be. You
generally don't want your OpenBSD partitions living outside the OpenBSD
MBR (fdisk) partition.
EXCEPT when the MBR isn't providing useful info. Like now.
...
At this point I'm wondering WTF is going on. Is this an OpenBSD-specific
problem? A BIOS issue? So I unplug all drives except one of the 3TB's,
install FreeBSD and tell it to use the whole drive. I get the exact same
results from their disklabel. Must be the hardware, right?
What you want to do is use the 'b' option of disklabel to redefine the
OpenBSD boundaries of the disk. I do believe it will let you specify
the whole disk, and you can then do what you want.
A few words of warning...
* This really messes up your ability to multiboot, as non-OpenBSD OSs
will think anything beyond the fdisk/MBR partition might be available.
But then, most other OSs choke pretty badly at this point anyway. may
not be that big a problem.
* Lots of BIOSes that see >128G disks still won't let you boot from
partitions higher than 128G.
* I haven't actually TRIED this. I was planning on buying a 3TB disk to
experiment on and update FAQ14...but just before I did, there was this
little flood issue, and being a cheapskate, I didn't want to sink a lot
of money into a drive I didn't really need quite yet (or more
accurately, I need TWO of...)
* Rebuilding the mirror will be a beast.
* you don't want to fsck a 3TB file system, 'specially if it is
rebuilding the mirror at the same time, though with 12G RAM, you might
be able to do it.
Nick.
