4MB extent VG limitations...

[Dave Cast]

Does anyone know off the top of their head what the VG max size limit is with 4mb extents set?

I've searched and searched and for some reason cannot find it -

v/r
Dave

[Pete Randall]

Wouldn't it depend on max_pe??? According to the vgcreate man page, max_pe can be up to 65535, making total size 65536*4MB. I'll let you do the math.


Pete

[Dave Cast]

Yeah - I started doing the math right after I posted this - I remember seeing a table online showing reccommended PE sizes -

I need a 4TB VG - according to my caculations - I'll need to set a 64MB PE size. Yikes.

[Torsten.]

This also depends on the LVM version, version 1.0 or 2.x ...

[Dave Cast]

I see talk of a 2TB limit in HPUX - is this the case?

[sangilak]

Hi,


Check the document below for details on the various limits for the different LVM versions 1.0, 2.x in HP-UX:
http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c01914836/c01914836.pdf

You can of course also check the limits on your system itself with the 'lvmadm' command:
# lvmadm -t


sangilak

[sangilak]

Whoops, forgot to copy/paste the actual output:

# lvmadm -t
--- LVM Limits ---
VG Version 1.0
Max VG Size (Tbytes) 510 <<<<<<<
Max LV Size (Tbytes) 16
Max PV Size (Tbytes) 2
Max VGs 256
Max LVs 255
Max PVs 255
Max Mirrors 2
Max Stripes 255
Max Stripe Size (Kbytes) 32768
Max LXs per LV 65535
Max PXs per PV 65535
Max Extent Size (Mbytes) 256

VG Version 2.0
Max VG Size (Tbytes) 2048 <<<<<<<
Max LV Size (Tbytes) 256
Max PV Size (Tbytes) 16
Max VGs 512
Max LVs 511
Max PVs 511
Max Mirrors 5
Max Stripes 511
Max Stripe Size (Kbytes) 262144
Max LXs per LV 33554432
Max PXs per PV 16777216
Max Extent Size (Mbytes) 256

VG Version 2.1
Max VG Size (Tbytes) 2048 <<<<<<<
Max LV Size (Tbytes) 256
Max PV Size (Tbytes) 16
Max VGs 2048
Max LVs 2047
Max PVs 2048
Max Mirrors 5
Max Stripes 511
Max Stripe Size (Kbytes) 262144
Max LXs per LV 33554432
Max PXs per PV 16777216
Max Extent Size (Mbytes) 256

[Norman_21]

Dave,

On an existing VG that I have in a system, it appears that I can increase the file system to 7TB but that will require renumbering the PE which may not be recommended by HP. However, this is an existing VG but in your case, you'll be creating a new one. Just wanted to share to give you an idea.


# vgmodify -t vgwhatever

Current Volume Group settings:
Max LV 255
Max PV 16
Max PE per PV 4357
PE Size (Mbytes) 8
VGRA Size (Kbytes) 624
VGRA space (Kbytes) without PE renumbering 896
VGRA space (Kbytes) PE renumbering lower 8192

Volume Group optimized settings (no PEs renumbered):
max_pv(-p) max_pe(-e) Disk size (Mb)
1 65535 524281
2 53756 430049
3 35836 286689
4 26876 215009
5 21500 172001
6 17916 143329
7 15356 122849
8 13308 106465
9 11772 94177
10 10748 85985
11 9724 77793
12 8956 71649
13 8188 65505
14 7676 61409
15 7164 57313
16 6652 53217
17 6140 49121
18 5884 47073
19 5628 45025
20 5372 42977
21 5116 40929
22 4860 38881
23 4604 36833

# vgmodify -t -n vgwhatever

Current Volume Group settings:
Max LV 255
Max PV 16
Max PE per PV 4357
PE Size (Mbytes) 8
VGRA Size (Kbytes) 624
VGRA space (Kbytes) without PE renumbering 896
VGRA space (Kbytes) PE renumbering lower 8192

Volume Group optimized settings (PEs renumbered lower):
max_pv(-p) max_pe(-e) Disk size (Mb)
15 65535 524288
16 63228 505832
17 59388 475112
18 56060 448488
19 53244 425960
20 50428 403432
21 48124 385000
22 45820 366568
23 44028 352232
24 41980 335848
25 40444 323560
26 38908 311272
27 37372 298984
28 36092 288744
29 34812 278504
30 33532 268264
31 32508 260072
32 31484 251880
33 30460 243688
34 29692 237544

# echo 524288*15|bc
7864320
# echo 7864320/1024|bc
7680

[Dave Cast]

# vgdisplay /dev/lv_images
--- Volume groups ---
VG Name /dev/vg_whatever
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 0
Open LV 0
Max PV 16
Cur PV 1
Act PV 1
Max PE per PV 16383
VGDA 2
PE Size (Mbytes) 128
Total PE 16383
Alloc PE 0
Free PE 16383
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0
VG Version 1.0.0

So it seems I have 1.0.0 which doesn't seem like it supports VG's above 2TB.

[chris huys_4]

Hi Dave,

Install the latest LVM command and kernel cumulative patches on HP-UX 11.23, which will up the max size of a volumegroup/logical volume to 16TB.

Patch Name: PHKL_40918

Patch Description: s700_800 11.23 LVM Cumulative Patch

[..]

No (superseded patches contained enhancements)

PHKL_36745:

This patch provides the kernel component for
the LVM Striped/Mirror and 16TB logical volume features. The Striped/Mirror LV feature allows the creation and use of logical volumes that are simultaneously striped and mirrored.

The 16TB LV feature allows accessing data
past the 2TB offset in logical volumes
(formerly logical volumes larger than 2TB could be created but could not be accessed beyond the 2TB boundary). To use these features, they must be explicitly enabled by installing PHCO_36746 or a superseding patch, because using them results in volume groups that are incompatible with prior releases and systems without these features. See the
Other Dependencies section of this document for the details.

Greetz,
Chris