You may have read of the new 4K Advanced Format drives now becoming popular on the market. In fact, if you’ve got a drive larger than 1 TB, you probably have one, even if you don’t know it. I’ve found lots of people assembling home NAS servers using 2 TB drives, linux software RAID or LVM, and all of them are concerned about aligning various parts of the storage infrastructure to the new 4K format. But, thanks to libblkid, you don’t have to.
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“How do I backup my BackupPC pool” is perhaps the most common topic of discussion on the backuppc-users mailing list. BackupPC stores all files in a common compressed pool (cpool, although I’ll use simply “pool” for this discussion), and maintains trees of hardlinks into the pool for each backup host. Therefore BackupPC requires a Linux/Unix filesystem. If you want to back up the BackupPC server itself, you must duplicate the pool, and the hardlinks to it.
Update 2012-01-18: This guide has been updated for recent changes, and is safe to use on current Ubuntu and Debian releases.
One of the reasons I started this blog is to write about problems I’ve solved that I can’t find answers to already on the web. Today, let’s talk about moving your linux install to linux software raid (md raid / mdadm). This post assumes you are running Ubuntu Linux 8.04, but any Debian-based distro from the past two years, or most other distros, will have similar commands.
We start with an install on a single 80 GB SATA drive, partitioned as follows:
/dev/sda1 as /, 10GB, ext3, bootable
/dev/sda2 as swap, 1GB
/dev/sda3 as /home, 69GB, ext3
We want to add a second 80GB SATA drive and move the entire install to use RAID1 between the two drives. So the final configuration will appear:
/dev/md0 as /, 10GB, ext3
/dev/md1 as swap, 1GB
/dev/md2 as /home, 69GB, ext3
Where the raid arrays are:
md0 : active raid1 sda1 sdb1
md1 : active raid1 sda2 sdb2
md2 : active raid1 sda3 sdb3
Here there be dragons. As always, back up your data first. If you don’t know how to use rsync, now is an excellent time to learn.