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developerWorks: Introduction to EVMS

Nov 04, 2002, 11:00 (0 Talkback[s])
(Other stories by Daniel Robbins)

"Have you ever stopped to think about how many powerful storage-related technologies are available for Linux? Consider just our options for a journaling filesystem: ReiserFS, ext3, XFS, and JFS. Several years ago, Linux didn't even have a journaling filesystem. Now, we have plenty of them and find ourselves in the luxurious position of being able to choose the best filesystem for our needs. Choice is definitely a good thing.

"Now let's think beyond mere filesystems. Linux's software RAID capabilities, which have been around for awhile, present another set of possibilities to the Linux admin (for more information, see Resources for links to my two-part series on Linux software RAID). And recently, we've been blessed with Sistina's Linux LVM technology (logical volume management; see Resources for links to my two-part LVM series and to download Sistina). LVM allows admins to manage their storage resources with much greater flexibly than the traditional method of using static disk partitions. With LVM, admins can expand and shrink filesystems on running servers and take advantage of other amazing capabilities, such as filesystem snapshots.

"So, taken as a whole, Linux has a tremendously rich set of storage-related technologies. And therein lies the problem; taken as a whole, we do have some great tools. But try to use several of these storage technologies together and things become complicated. For example, let's imagine that we want to create a ReiserFS filesystem that sits upon an LVM logical volume (so that it can be dynamically expanded as needed), which in turn sits upon a RAID-1 software RAID volume (in order to provide some protection against disk failure)..."

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