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Old 10-15-2008, 02:36 AM
Craig White
 
Default formatting large volume

I just got a new server with a Dell MD-1000 SAS unit and 6-750 gigabyte
drives which are now initializing in RAID 10 which will give me just
about 2 terabytes.

I vaguely recall reading that fdisk wasn't suitable for partitioning and
wonder if I shouldn't be using partd instead. I am also wondering if I
should use lvm or just mkfs to create the filesystem. Anyone have
suggestions before I blunder in?

Thanks

Craig

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Old 10-15-2008, 03:06 AM
"Joseph L. Casale"
 
Default formatting large volume

>I vaguely recall reading that fdisk wasn't suitable for partitioning and
>wonder if I shouldn't be using partd instead. I am also wondering if I
>should use lvm or just mkfs to create the filesystem. Anyone have
>suggestions before I blunder in?

fdisk can't do GPT which is what you need for partitions larger than
2tb, so you use parted w/ gpt.

If it were mine, I'd partition it as one big chunk and mark it LVM, then carve
it out so you have the flexibility. After all, you already made it one array so
making partitions out of it only limits you down the road.

YMMV,
jlc
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Old 10-15-2008, 01:47 PM
Ross Walker
 
Default formatting large volume

On Oct 14, 2008, at 10:36 PM, Craig White <craigwhite@azapple.com>
wrote:


I just got a new server with a Dell MD-1000 SAS unit and 6-750
gigabyte

drives which are now initializing in RAID 10 which will give me just
about 2 terabytes.

I vaguely recall reading that fdisk wasn't suitable for partitioning
and

wonder if I shouldn't be using partd instead. I am also wondering if I
should use lvm or just mkfs to create the filesystem. Anyone have
suggestions before I blunder in?


Just pvcreate the whole disk and forgo partitioning it. Then create a
vg out of it and start creating lvs.


-Ross

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Old 10-15-2008, 02:15 PM
"Joseph L. Casale"
 
Default formatting large volume

>Just pvcreate the whole disk and forgo partitioning it. Then create a
>vg out of it and start creating lvs.

Hey Ross,
I thought it was best practice to create an LVM partition such that the
disk could be recognizable under all circumstances such as if the volume
was moved? Is that not really "best practice" anymore?

jlc
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Old 10-15-2008, 04:52 PM
Craig White
 
Default formatting large volume

On Wed, 2008-10-15 at 09:47 -0400, Ross Walker wrote:
>
> On Oct 14, 2008, at 10:36 PM, Craig White <craigwhite@azapple.com>
> wrote:
>
> > I just got a new server with a Dell MD-1000 SAS unit and 6-750
> > gigabyte
> > drives which are now initializing in RAID 10 which will give me just
> > about 2 terabytes.
> >
> > I vaguely recall reading that fdisk wasn't suitable for partitioning
> > and
> > wonder if I shouldn't be using partd instead. I am also wondering if I
> > should use lvm or just mkfs to create the filesystem. Anyone have
> > suggestions before I blunder in?
>
> Just pvcreate the whole disk and forgo partitioning it. Then create a
> vg out of it and start creating lvs.
----
OK - makes sense but I am a bit confused here.

I have done the pgcreate and tested lvcreate but wonder about
'setphysicalextentsize' because in the man page, it states, "The default
of 4 MB leads to a maximum logical volume size of around 256GB" which
makes me think that if I want one volume when this is all done, I have
to increase that value.

# fdisk -l /dev/sdb

Disk /dev/sdb: 2248.8 GB, 2248818032640 bytes
255 heads, 63 sectors/track, 273403 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdb doesn't contain a valid partition table

So thinking that I would need a volume just under 10 times the maximum
of 256GB, I would have to set the physicalextentsize to 64 MB (32 not
being quite large enough and thus 64 being the next increment in power
of 2)

Does this make sense?

Craig

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Old 10-15-2008, 05:34 PM
Stephen Harris
 
Default formatting large volume

On Wed, Oct 15, 2008 at 09:52:03AM -0700, Craig White wrote:
> I have done the pgcreate and tested lvcreate but wonder about
> 'setphysicalextentsize' because in the man page, it states, "The default
> of 4 MB leads to a maximum logical volume size of around 256GB" which
> makes me think that if I want one volume when this is all done, I have
> to increase that value.

The man page for "vgcreate" says "there is a limit of 65534 extents in
each logical volume" but only for *lvm1* format. lvm2 format doesn't
have such restrictions.

I used default values for my 4Tbyte array (5*1Tbyte disk in a md raid5)
under CentOS 4.

% fdisk -l /dev/md3

Disk /dev/md3: 4000.8 GB, 4000808697856 bytes
2 heads, 4 sectors/track, 976759936 cylinders
Units = cylinders of 8 * 512 = 4096 bytes


% pvdisplay /dev/md3
--- Physical volume ---
PV Name /dev/md3
VG Name Raid5
PV Size 3.64 TB / not usable 320.00 KB
Allocatable yes (but full)
PE Size (KByte) 4096
Total PE 953867
Free PE 0
Allocated PE 953867
PV UUID NngvXK-4tqJ-xNtG-UnDL-Rin0-RHIl-xZ2wzI

% vgdisplay Raid5
--- Volume group ---
VG Name Raid5
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 1
Act PV 1
VG Size 3.64 TB
PE Size 4.00 MB
Total PE 953867
Alloc PE / Size 953867 / 3.64 TB
Free PE / Size 0 / 0
VG UUID mKSI0h-26i7-5LK5-vwpX-GY3a-Bjiv-xX4q8n

% lvdisplay Raid5/Media
--- Logical volume ---
LV Name /dev/Raid5/Media
VG Name Raid5
LV UUID c8x4Ip-R1wq-n9An-NM6B-IuBs-U61L-kfVgAU
LV Write Access read/write
LV Status available
# open 1
LV Size 3.64 TB
Current LE 953867
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:5


> Does this make sense?

Try using "pvcreate", "vgcreate" and "lvcreate" with no special options
and see what happens. It worked for me!

The default in CentOS should be lvm2; you can see that's what was
created on mine by the "Format" line in the vgdisplay output.

Format lvm2

--

rgds
Stephen
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Old 10-15-2008, 06:13 PM
Craig White
 
Default formatting large volume

On Wed, 2008-10-15 at 13:34 -0400, Stephen Harris wrote:
> On Wed, Oct 15, 2008 at 09:52:03AM -0700, Craig White wrote:
> > I have done the pgcreate and tested lvcreate but wonder about
> > 'setphysicalextentsize' because in the man page, it states, "The default
> > of 4 MB leads to a maximum logical volume size of around 256GB" which
> > makes me think that if I want one volume when this is all done, I have
> > to increase that value.
>
> The man page for "vgcreate" says "there is a limit of 65534 extents in
> each logical volume" but only for *lvm1* format. lvm2 format doesn't
> have such restrictions.
>
> I used default values for my 4Tbyte array (5*1Tbyte disk in a md raid5)
> under CentOS 4.
>
SNIP...
>
> Try using "pvcreate", "vgcreate" and "lvcreate" with no special options
> and see what happens. It worked for me!
>
> The default in CentOS should be lvm2; you can see that's what was
> created on mine by the "Format" line in the vgdisplay output.
>
> Format lvm2
----
OK - well, I can delete the vg and the lv that I created and just
consider them as practice. I'm not really sure what the difference would
be having the physical extent size as 64 MB versions 4 MB.

I did run into a snag that I don't fully understand while trying to make
the filesystem though...

# mke2fs -v -j -l 2TbVol /dev/VolGroup10/2TbVol
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
274513920 inodes, 549011456 blocks
27450572 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
16755 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616,
78675968,
102400000, 214990848, 512000000

read_bad_blocks_file: No such file or directory while trying to open
2TbVol

Obviously there is no physical disk to read a bad blocks file from and I
don't see in the man page for mke2fs any way to tell it to ignore bad
blocks or not search for the file.

Craig

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Old 10-15-2008, 06:31 PM
"Joseph L. Casale"
 
Default formatting large volume

>I'm not really sure what the difference would
>be having the physical extent size as 64 MB versions 4 MB.

It's the smallest allocatable size of any PV you can give to an LV.
Think of it like Allocation Unit Size. Also as pointed out above some
limitations arise in different versions of LVM. RH defaults to 32M I
believe...
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Old 10-15-2008, 06:34 PM
Stephen Harris
 
Default formatting large volume

On Wed, Oct 15, 2008 at 11:13:08AM -0700, Craig White wrote:
> I did run into a snag that I don't fully understand while trying to make
> the filesystem though...
>
> # mke2fs -v -j -l 2TbVol /dev/VolGroup10/2TbVol

Were you trying to specify a label? If so, use the -L option, not -l

Were you trying to specify a bad block list? Why? I'd be VERY surprised
if you need to do this.

So you either meant
mke2fs -v -j /dev/VolGroup10/2TbVol
OR
mke2fs -v -j -L 2TbVol /dev/VolGroup10/2TbVol

--

rgds
Stephen
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Old 10-15-2008, 06:42 PM
Craig White
 
Default formatting large volume

On Wed, 2008-10-15 at 14:34 -0400, Stephen Harris wrote:
> On Wed, Oct 15, 2008 at 11:13:08AM -0700, Craig White wrote:
> > I did run into a snag that I don't fully understand while trying to make
> > the filesystem though...
> >
> > # mke2fs -v -j -l 2TbVol /dev/VolGroup10/2TbVol
>
> Were you trying to specify a label? If so, use the -L option, not -l
>
> Were you trying to specify a bad block list? Why? I'd be VERY surprised
> if you need to do this.
>
> So you either meant
> mke2fs -v -j /dev/VolGroup10/2TbVol
> OR
> mke2fs -v -j -L 2TbVol /dev/VolGroup10/2TbVol
----
duh...thanks :::blush:::

too many man pages ;-)

Thanks

Craig

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