Notes from CentraLUG, 2-April-2007: Bill Stearns on LVM

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 GNHLUG’s archival sites. Add one of these to your favorite RSS readers to see the GNHLUG announcements: mail-archive.com or gmane.org

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.

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) and handled some questions further afield, like the file defragmenter Bill has on his site.

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.

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