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Update vgcreate man page.

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Alasdair Kergon 2005-01-19 17:01:18 +00:00
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WHATS_NEW
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@ -1,5 +1,6 @@
Version 2.01.01 -
===================================
Update vgcreate man page.
Version 2.01.00 - 17th January 2005
===================================

50
man/vgcreate.8
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@ -33,29 +33,44 @@ previously configured for LVM with
.SH OPTIONS
See \fBlvm\fP for common options.
.TP
.BR \-A ", " \-\-autobackup " {" y | n }
Controls automatic backup of VG metadata after the change (see
.BR vgcfgbackup (8)).
Default is yes.
.TP
.BR \-l ", " \-\-maxlogicalvolumes " " \fIMaxLogicalVolumes\fR
Sets the maximum possible logical volume count.
More logical volumes can't be created in this volume group.
Absolute maximum is 256.
Sets the maximum number of logical volumes allowed in this
volume group.
The setting can be changed with \fBvgchange\fP.
For volume groups with metadata in lvm1 format, the limit
and default value is 255.
If the metadata uses lvm2 format, the default value is 0
which removes this restriction: there is then no limit.
.TP
.BR \-p ", " \-\-maxphysicalvolumes " " \fIMaxPhysicalVolumes\fR
Sets the maximum possible physical volume count.
More physical volumes can't be included in this volume group.
Absolute maximum is 256.
Sets the maximum number of physical volumes that can belong
to this volume group.
The setting can be changed with \fBvgchange\fP.
For volume groups with metadata in lvm1 format, the limit
and default value is 255.
If the metadata uses lvm2 format, the default value is 0
which removes this restriction: there is then no limit.
If you have a large number of physical volumes in
a volume group with metadata in lvm2 format,
for tool performance reasons, you should consider
some use of \fB--metadatacopies 0\fP
as described in \fBpvcreate(8)\fP.
.TP
.BR \-s ", " \-\-physicalextentsize " " \fIPhysicalExtentSize\fR[\fBkKmMgGtT\fR]
Sets the physical extent size on physical volumes of this volume group.
A size suffix (k for kilobytes up to t for terabytes) is optional, megabytes
is the default if no suffix is present. Values can be from 8 KB to 16 GB in
powers of 2. The default of 4 MB causes maximum LV sizes of ~256GB because as
many as ~64k extents are supported per LV. In case larger maximum LV sizes are
needed (later), you need to set the PE size to a larger value as well. Later
changes of the PE size in an existing VG are not supported.
powers of 2. The default is 4 MB.
Once this value has been set, it is difficult to change it without recreating
the volume group which would involve backing up and restoring data on any
logical volumes.
If the volume group metadata uses lvm1 format, there is a limit of 65534
extents in each logical volume, so the default of 4 MB leads to a maximum
logical volume size of around 256GB.
If the volume group metadata uses lvm2 format there is no such restriction,
although having a large number of extents will slow down
the tools but have no impact on I/O performance to the logical volume.
The 2.4 kernel has a limitation of 2TB per block device.
.SH EXAMPLES
To create a volume group named
.B test_vg
@ -67,11 +82,6 @@ with default physical extent size of 4MB:
\ vgcreate test_vg /dev/sdk1 /dev/sdl1
.fi
To limit kernel memory usage, there is a limit of 65536 physical extents
(PE) per logical volume, so the PE size determines the maximum logical volume
size. The default PE size of 4MB limits a single logical volume to 256GB (see
the -s option to raise that limit).
There is also (as of Linux 2.4) a kernel limitation of 2TB per block device.
.SH SEE ALSO
.BR lvm (8),
.BR pvdisplay (8),