From: Corné Beerse (cbeerse@lycos.nl)
Date: Wed May 19 2004 - 05:46:05 EDT
Lodge, David wrote:
> It always takes a while to wrap your head around LVM, but its quite simple:
Your list is simpel enough but I mis 'partitions' in the list. I can see them at
2 places:
>
> 1. Physical Volumes (PV): These are either hard discs or a RAID group that
> represents one device to the system - these can be seen on an 'ioscan' as
> (for example) /dev/dsk/c0t5d0.
These PVs can also be partitions of the above disks. Since some systems put
disk-administration in the parition table, the phisical disk or the raid-group
or whatever, will be partitioned. Most likely, a sinlge partition that spans the
entire disk.
> 2. Volume Groups (VG): These are a collection of one or more PVs; these are
> to allow a greater flexibility in management of disc space, and to aid with
> clustering, for example if you had 2 databases on a system you may make one
> VG for database1 and another for database2. The volume group is a directory
> under /dev which contains a group file which defines the major and minor
> numbers
> 3. Logical Volumes (LV): These are what are actually used as by the system,
> these may be either raw partitions (eg for use by a database) or have a
> filing system on.
Once again, since the OS accesses these logical volumes as (virtual) disks,
these logical volumes will be paritioned for the sake of disk-administration.
Here the advice is a little less hard but still: create a single partition that
spans the entire logical volume. At this level, parititioning in multiple
partitions is accepted since it will contain the filesystems and a lot of OS-es
default to multiple filesystems on a sinlge disk.
> 4. Filing System (FS): These are placed on LVs. These are what you mount.
That is to say, a partition in the LV. Basically for ease of administration (the
filesystem type is in the partition table), optionally for subdeviding the LV
into different partitions.
>
> For mounting the new disk; check the vgscan manpage as this will read the
> LVM information from the disk and will allow you to reinsert it back into
> the system
THere are some slight differences between HP-UX lvm and Linux lvm. I might mix
them, specially in case of the parition table in the physical volume.
>
> HTH
>
> dave
>
>
>>-----Original Message-----
>>From: Roy Kidder [mailto:RoyKidder@yahoo.com]
>>Sent: 16 May 2004 23:42
>>To: hpux-admin@DutchWorks.nl
>>Subject: [HPADM] disk and file system help
>>
>>
>>Admins-
>>
>>I'm new to HP-UX and am trying to wrap my head around the
>>concepts of volume groups and logical volumes versus
>>partitions as well as the different local file systems that
>>HP-UX supports.
>>
>>Is there anywhere to get a good definition between all of these?
>>
>>Also -- in a practical application -- I have a single disk
>>that has a single file system on it which I am adding to an
>>existing machine running 11.0. The system sees the physical
>>disk at 8/4.11.0. The problem is that I have no idea how to
>>mount it. I have no idea what file system it's using, except
>>to say that it came out of another 11.0 box.
>>
>>Thanks in advance,
>>Roy
>>
>>
>>
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>
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