CentraLUG Notes, 2-April-2007: Bill Stearns and LVM

Ted Roche tedroche at tedroche.com
Tue Apr 3 20:06:22 EDT 2007


A great meeting last night. The Central New Hampshire Linux User Group
met at the usual place and time: The New Hampshire Technical Institute's
Library, Room 146, 7PM on the first Monday.

I did my usual rounds of announcements, Shawn O'Shea pointed out that
besides for the discuss and announce mailing lists, you can also
subscribe to the lists via RSS by using one of our archival sites. Add
of the following to your favorite RSS readers to see the GNHLUG
announcements:

http://www.mail-archive.com/gnhlug-announce@mail.gnhlug.org/maillist.xml

http://rss.gmane.org/messages/excerpts/gmane.org.user-groups.linux.gnhlug.announce

Everyone got to introduce themselves and speak a little bit about what
they're up to. I passed around a couple lists of topics and speakers
from the wiki to find out what the attendees want to see for future
sessions.

Bill Stearns presented "LVM: Logical Volume Management." He explained
about the basic need to expand or re-allocate disk resources without
making hard partition changes, in some cases without even shutting down.
We started right in on an exercise: using the loopback device and some
spare space in /var/tmp, we created three loopback block devices. We
assigned them as PVs (Physical Volumes) and allocated two to a Volume
Group. Then, space could be allocated out of the volume group to provide
the space needed. Additional PVs could be added to the VG, additional
space from the VG could be allocated to a mount. We had a good
discussion about the choice of filesystems and the different processing
required for ext3, reiser, xfs, jfs file systems - most of which can be
resized when on-line. (Bill recommended the MythTV HOWTO for a good
discussion of which file system to use. This one, I think:

http://mythtv.org/docs/mythtv-HOWTO-24.html#ss24.1

We had a good side conversation at this point about the mount tables and
the significance of several flags Bill had. An intesnse discussion of
'noatime' - useful for hierarchical file management, but generally of
little use, and a lot of disk activity, power consumption, speed
decrease, and for FlashROM devicers, perhaps lifetime shortening can be
avoided by adding noatime to the mount tab. Bill also had war stories
about the security implications of nodev and nosuid both of which are a
good idea for insertable media unless you have a specific reason for
needing them.

We finished up the LVM exercise by adding the third PV to the VG and
then resizing the ext3 partition to include the space. Bill took
questions from the audience: one lady had just installed LVM on the
Linux partition on her mainframe (!) that weekend, and wanted to know
more about LVM striping. Other questions on reliability, use with RAID.
Bill had some pointers for adding additional storage: use of USB2 (not
USB1!) external drives (Bill hasn't been happy with Firewire storage on
Linux) or using an external storage solution (he mentioned CoRAID which
uses rackable ethernet-to-ATA raw drives; Bill had one sample to play
with - http://www.coraid.com/) and handled some questions further
afield, like the file defragmenter Bill has on his site
(http://www.stearns.org/defragfile/)

Yet another great LUG meeting. Thanks to Bill Stearns for the great
presentation (and 3-ring-bound handouts) and providing the raffle door
prizes. Thanks to Bill Sconce for providing the projector and doing the
note-taking during the meeting. Thanks to the New Hampshire Technical
Institute for providing the facilities.

Look forward to a great presentation on OpenWRT by Ben Scott at the May
7th meeting (where you can expect him to be heckled) and another great
presentation on Drupal by Seth Cohn on June 4th. Hope to see you there.

Ted Roche
Ted Roche & Associates, LLC
http://www.tedroche.com


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