Jeff Darcy wrote:
On 12/27/12 6:47 PM, Miles Fidelman wrote:
John Mark Walker wrote:
In general, I don't recommend any distributed filesystems for VM
images, but I can also see that this is the wave of the future.
Ok. I can see that.
Let's say that I take a slightly looser approach to high-availability:
- keep the static parts of my installs on local disk
- share and replicate dynamic data using gluster
That, in a nutshell, is the approach that I (and others) often advocate. Block
storage should be used sparingly, e.g. for booting and for data served to
others at a higher level. I'd say that's true in general, but it's especially
true for any kind of network block storage. When network latencies are
involved, going "up the stack" where operations are expressed at a high
semantic level will almost always work out better than blocks and locks.
What's the alternative, though? Ok, for application files (say a word
processing document) that works, but what about spools, databases, and
such? Seems like blocks are the common denominator.
- data is triply replicated (allow for 2-node failures)
Unfortunately, three-way replication is still a bit of a work in progress.
Some (such as Joe Julian) use it successfully, but they also use it very
carefully. I've had to make a few fixes in this area myself recently, and I
expect to make a few more before I'd say that it's really up to snuff for
general use.
That's a bit disappointing. For high-availability applications (like
mine), 3-way replication would seem to be the major advantage of a
cluster file system over DRBD.
Thanks,
Miles Fidelman
--
In theory, there is no difference between theory and practice.
In practice, there is. .... Yogi Berra
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