From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx02.extmail.prod.ext.phx2.redhat.com [10.5.110.6]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id n9K0QgmQ009036 for ; Mon, 19 Oct 2009 20:26:42 -0400 Received: from mail-gx0-f226.google.com (mail-gx0-f226.google.com [209.85.217.226]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n9K0QWQ5003228 for ; Mon, 19 Oct 2009 20:26:32 -0400 Received: by gxk26 with SMTP id 26so3034635gxk.11 for ; Mon, 19 Oct 2009 17:26:32 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 19 Oct 2009 20:26:32 -0400 Message-ID: Subject: Re: [linux-lvm] Total free space using added VGs and LVs From: Lou Arnold Content-Type: multipart/alternative; boundary=001636ed67760325ce047652ea55 Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: To: Drew Cc: LVM general discussion and development --001636ed67760325ce047652ea55 Content-Type: text/plain; charset=ISO-8859-1 Yes, OK, I see the advantage in your examples. I've tried this (add a drive to VolGroup00/LogVol00) and it certainly works, but it is much more difficult to undo than 1) creating a new volume group and new volume, or 2) adding the drive to VolGroup00 and creating a new volume. I read the documentation, but the file system fails whenever I reboot. After all, LogVol00 is mounted at root, you can't unmount root to shrink the volume. If you assume that the drive is empty and so you don't have any data to migrate, how does one do it? On 10/19/09, Drew wrote: > > >> > 1) Why would you want several logical volumes in one volume group? > >> > >> The same reason(s) you would want to partition a regular hard drive. > >> > >> Maybe you only want /home to have 20GB so your kids can't flood the > >> computer with downloaded music. Maybe you want /var/www to have > >> restricted permissions so your home web server is less vulnerable to > >> hackers. Maybe you're running a PVR application like MythTV and want a > >> high-performance filesystem like XFS for storing recorded shows. > >> > >> All of these can be done with logical volumes, and are often easier > under > >> LVM. > > > > > > But then if the above is true, then you may as well simply mount the > > partition as normal and add an entry into the fstab file. You get no > > advantage one way or the other - is that true? > > LVM does this better then regular disk partitioning. The fact that it > creates a pool of space is it's power. > > Two examples. > > Let's say you don't have LVM and partitioned your disk with some > leftover space. What happens if you change your mind and want to > increase the size of a partition? Now you have to juggle the > partitions on the disk while you move that free space around to a > place where the partition can be extended. I've done it before and > it's messy. LVM? Just use the lvextend command with the right > parameters and you're done. > > Next. Say you have two 80GB disks each partitioned with two partitions > 60GB & 20GB. Now say you need to add an extra partition 30GB in size. > How? With regular disks, you pretty much can't. With LVM, you'd have > 40GB free and can just create the 30GB logical volume without worrying > about which disk. > > As a side note, can you cc: the LVM list when you reply? I don't think > they're getting your side of this conversation. > > > -- > Drew > > "Nothing in life is to be feared. It is only to be understood." > --Marie Curie > --001636ed67760325ce047652ea55 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Yes, OK, I see the advantage in your examples.
=A0
I've tried this (add a drive to VolGroup00/LogVol00) and it certai= nly works, but it is much more difficult to undo than 1) creating a new vol= ume group and new volume, or 2) adding the drive to VolGroup00 and creating= a new volume. I read the documentation, but the file system fails whenever= I reboot. After all, LogVol00 is mounted at root, you can't unmount ro= ot to=A0shrink the volume. If you assume that the drive is empty and so you= don't have any data to migrate, how does one do it?

=A0
On 10/19/09, Drew <drew.kay@gmail.com&= gt; wrote:
>> > 1) Why would you w= ant several logical volumes in one volume group?
>>
>> Th= e same reason(s) you would want to partition a regular hard drive.
>>
>> Maybe you only want /home to have 20GB so your kids ca= n't flood the
>> computer with downloaded music. Maybe you wan= t /var/www to have
>> restricted permissions so your home web serv= er is less vulnerable to
>> hackers. Maybe you're running a PVR application like MythTV an= d want a
>> high-performance filesystem like XFS for storing recor= ded shows.
>>
>> All of these can be done with logical vo= lumes, and are often easier under
>> LVM.
>
>
> But then if the above is true, then y= ou may as well simply mount the
> partition as normal and add an entr= y into the fstab file. You get no
> advantage one way or the other - = is that true?

LVM does this better then regular disk partitioning. The fact that itcreates a pool of space is it's power.

Two examples.

Le= t's say you don't have LVM and partitioned your disk with some
leftover space. What happens if you change your mind and want to
increas= e the size of a partition? Now you have to juggle the
partitions on the = disk while you move that free space around to a
place where the partitio= n can be extended. I've done it before and
it's messy. LVM? Just use the lvextend command with the right
parame= ters and you're done.

Next. Say you have two 80GB disks each par= titioned with two partitions
60GB & 20GB. Now say you need to add an= extra partition 30GB in size.
How? With regular disks, you pretty much can't. With LVM, you'd hav= e
40GB free and can just create the 30GB logical volume without worrying=
about which disk.

As a side note, can you cc: the LVM list when = you reply? I don't think
they're getting your side of this conversation.


--
Drew
"Nothing in life is to be feared. It is only to be understood.&q= uot;
--Marie Curie

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