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Old 07-30-2010, 09:16 PM
Ron Blizzard
 
Default When should LVM be used?

On Fri, Jul 30, 2010 at 8:33 AM, Todd Denniston
<Todd.Denniston@tsb.cranrdte.navy.mil> wrote:

> Best use for LVM I have seen...
> Reducing the number of times you need to enter the LUKS pass phrase to once per boot, i.e., one LUKS
> containing an LVM of / and Swap so that the system can boot with one entry of the pass phrase and if
> you then have other partitions, such as an independent /home, /etc/crypttab can be used (with
> appropriately constructed and protected cryptpassphrase files).

At this point I don't even know what a LUKS pass phrase is -- is this
something I'm liable to run into on a home desktop computer?

--
RonB -- Using CentOS 5.5
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Old 07-30-2010, 09:31 PM
Whit Blauvelt
 
Default When should LVM be used?

On Fri, Jul 30, 2010 at 04:11:17PM -0500, Ron Blizzard wrote:

> Is there any way to mount an LVM partition from another Linux distribution?

Yes. They all support it. You might have to install a package for it, but
it's been standard for a few years pretty much across the board.

Whit
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Old 07-30-2010, 09:32 PM
Robert Heller
 
Default When should LVM be used?

At Fri, 30 Jul 2010 16:07:39 -0500 CentOS mailing list <centos@centos.org> wrote:

>
> On Fri, Jul 30, 2010 at 5:50 AM, Juergen Gotteswinter <jg@internetx.de> wrote:
>
> > * snaphotting (great for db backup)
> > * resizing partition
> > * "online" partitioning
>
> I didn't know LVM would do snapshots -- I'll have to look into that.
> But I'm guessing the feature is pretty much worthless if the whole
> hard drive is taken up by one LVM partition -- which has been my
> CentOS default setups.

Yes, the *default* setup is just plain wrong, and in general should NOT
be used. Yes, the default works (one big happy filesystem), and
actually might make sense for a virtual server, but otherwise no. See

http://www.deepsoft.com/2006/03/partitioning-for-linux/

for some thoughts on partitioning for Linux (also applies to LVM volumes).

>
> Thanks.
>

--
Robert Heller -- Get the Deepwoods Software FireFox Toolbar!
Deepwoods Software -- Linux Installation and Administration
http://www.deepsoft.com/ -- Web Hosting, with CGI and Database
heller@deepsoft.com -- Contract Programming: C/C++, Tcl/Tk

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Old 07-31-2010, 04:12 AM
JohnS
 
Default When should LVM be used?

On Fri, 2010-07-30 at 17:32 -0400, Robert Heller wrote:
> Yes, the *default* setup is just plain wrong, and in general should NOT
> be used. Yes, the default works (one big happy filesystem), and
> actually might make sense for a virtual server, but otherwise no. See

Yea the default works but how is it Plain Wrong? If it was flat out
wrong then Upstream would not allow it. Raid 1 disk array with one hot
spare on a hardware raid controller under a SAN server is what you
saying is wrong? Case is, the array is not using /home or /var; were
only exporting nfs luns direct attached. What on earth and why would I
want to have another drive for /var &/home in this case. I'm just
asking but not arguing. There are cases where it works exceptionally.
In fact my opinion is it works nice for newbies, untill they gets a lil
experience.

> http://www.deepsoft.com/2006/03/partitioning-for-linux/

With number one I do not agree. You can install apps under winblows in
any location. Not every Unix/Linux system has the same file layout.
Debian vs CentOS

John

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Old 07-31-2010, 12:32 PM
Drew
 
Default When should LVM be used?

> Yea the default works but how is it Plain Wrong? *If it was flat out
> wrong then Upstream would not allow it. *Raid 1 disk array with one hot
> spare on a hardware raid controller under a SAN server is what you
> saying is wrong? *Case is, the array is not using /home or /var; were
> only exporting nfs luns direct attached. *What on earth and why would I
> want to have another drive for /var &/home in this case. *I'm just
> asking but not arguing. *There are cases where it works exceptionally.
> In fact my opinion is it works nice for newbies, untill they gets a lil
> experience.

I'd still want a separate partition for /var for the SAN
configuration. I've seen more then one machine brought to it's knees
by overflowing log entries.



--
Drew

"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
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Old 07-31-2010, 01:52 PM
Drew
 
Default When should LVM be used?

> Is there any reason to use LVM on a personal desktop install of
> CentOS? It seems to me, for my purposes, that LVM is just a pain in
> the neck -- although I've always just let CentOS set it up during the
> install in the past. *I would like to be able to use parted to resize
> partitions when I want to, and also I'd like Vector Linux to be able
> to read and write data to the CentOS partition. Would I be missing
> something by not installing LVM, or is this mostly for server purposes
> anyhow?

LVM adds flexability that regular partitioning can't.

Example 1. Say you've mounted an entire 2TB disk as /home and it's
almost full. Now you want to add another 2TB to /home. How do you?
Easiest way is with LVM. You just add the new disk into LVM's pool of
storage and expand the home partition (Logical volume) to use the new
space. Now you have a single filesystem spread across two disks.

Example 2. Now let's say that you bought a NAS device (QNAP, Drobo,
Buffalo) that does iSCSI or NFS and you want to move your data off the
two local disks. With LVM you just add the new 'disk' into the pool
then tell LVM to move existing data off the 'old' disk.

Try doing that with parted. :-P

--
Drew

"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
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Old 08-01-2010, 01:35 PM
JohnS
 
Default When should LVM be used?

On Sat, 2010-07-31 at 05:32 -0700, Drew wrote:
> > Yea the default works but how is it Plain Wrong? If it was flat out
> > wrong then Upstream would not allow it. Raid 1 disk array with one hot
> > spare on a hardware raid controller under a SAN server is what you
> > saying is wrong? Case is, the array is not using /home or /var; were
> > only exporting nfs luns direct attached. What on earth and why would I
> > want to have another drive for /var &/home in this case. I'm just
> > asking but not arguing. There are cases where it works exceptionally.
> > In fact my opinion is it works nice for newbies, untill they gets a lil
> > experience.
>
> I'd still want a separate partition for /var for the SAN
> configuration. I've seen more then one machine brought to it's knees
> by overflowing log entries.
---
I can't really argue that point there. I've seen iptables do the same
as also auditd. Carefulness in log watching is the key. You check your
logs?

John

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Old 08-02-2010, 02:26 PM
Todd Denniston
 
Default When should LVM be used?

Ron Blizzard wrote, On 07/30/2010 05:16 PM:
> On Fri, Jul 30, 2010 at 8:33 AM, Todd Denniston
> <Todd.Denniston@tsb.cranrdte.navy.mil> wrote:
>
>> Best use for LVM I have seen...
>> Reducing the number of times you need to enter the LUKS pass phrase to once per boot, i.e., one LUKS
>> containing an LVM of / and Swap so that the system can boot with one entry of the pass phrase and if
>> you then have other partitions, such as an independent /home, /etc/crypttab can be used (with
>> appropriately constructed and protected cryptpassphrase files).
>
> At this point I don't even know what a LUKS pass phrase is -- is this
> something I'm liable to run into on a home desktop computer?
>

Depends on how much you value not letting other folks at your data, with out your permission after
you have properly powered down the machine.

LUKS is used with encrypted partitions/filesystems. I have only used it at the partition level.
It is most easily setup at install time, because anaconda gets the incantations correct for you.

Suggested further reading:
http://wiki.centos.org/HowTos/EncryptedFilesystem
http://wiki.centos.org/TipsAndTricks/EncryptedFilesystem/Scripts
http://en.wikipedia.org/wiki/Linux_Unified_Key_Setup

--
Todd Denniston
Crane Division, Naval Surface Warfare Center (NSWC Crane)
Harnessing the Power of Technology for the Warfighter
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Old 08-03-2010, 01:20 AM
Drew
 
Default When should LVM be used?

On Sun, Aug 1, 2010 at 6:35 AM, JohnS <jses27@gmail.com> wrote:
>
> On Sat, 2010-07-31 at 05:32 -0700, Drew wrote:
>>
>> I'd still want a separate partition for /var for the SAN
>> configuration. I've seen more then one machine brought to it's knees
>> by overflowing log entries.
> ---
> I can't really argue that point there. *I've seen iptables do the same
> as also auditd. *Carefulness in log watching is the key. *You check your
> logs?
>
> John

I do. Daily emails with copies of all logs and a summary disk usage
statement of all partitions.

I learned my lesson about log files a while back. ;-)


--
Drew

"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
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Old 08-04-2010, 10:35 AM
Michael Simpson
 
Default When should LVM be used?

On 31 July 2010 14:52, Drew <drew.kay@gmail.com> wrote:
>> Is there any reason to use LVM on a personal desktop install of
>> CentOS? It seems to me, for my purposes, that LVM is just a pain in
>> the neck -- although I've always just let CentOS set it up during the
>> install in the past. *I would like to be able to use parted to resize
>> partitions when I want to, and also I'd like Vector Linux to be able
>> to read and write data to the CentOS partition. Would I be missing
>> something by not installing LVM, or is this mostly for server purposes
>> anyhow?
>
> LVM adds flexability that regular partitioning can't.
>

Just to add some more info to the conversation.
Yesterday i found out that if you have a modern SSD and are planning
on using RHEL6 or CentOS6 then LVM will not support the "TRIM" ATA
command thus there will be a significant decrease in the write
perfomnace of the drive with time. Linux swap will use it but the only
way to enable this feature is if your partitions are native ext4 and
you use the "discard" option.

Thus TRIM will not be enabled by a default install except for swap space.

mike
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