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Saturday, July 17th, 2004

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drbd, nbd, ha storage etc.
I'm looking to leverage one of the network block device like technologies to create a mirrored array over the wire for data redundancy. I've noted at least three competing OSS technologies in this arena.

  1. Original nbd.

  2. Enhanced NBD

  3. DRBD

At first glance it appears that drbd has the edge on the competition for my purposes since it is optimized to do exactly what I want it to do. For instance, it has it's own abstraction layer to create the mirror and does not rely on generic MD which treats all devices as equal. So with DRBD, only the writes are sent over the wire to the replica while all reads are done on the local disk.

Ok... Onto the question.

Are any of you using these technologies or similar technologies (even proprietary). If so, what variants, application details, etc. What's you impression of the solution your using. Also, if you know of a similar solution that I haven't mentioned here, please tell me what it is even if you do not have experience with it. I really want to consider all the possibilities in this early planning phase.
Help! I don't want to reboot!
I've been in an experimental mood today and I wrote a script that seems to have made my cd-rom get hung up. Basically, the script sent a "mount /dev/cdrom /mnt/cdrom", I got the message that it had mounted read-only, but at that point the script stopped. Looking at the processes (ps ax), I can see that the mount is still active. But I cannot kill -9 the process. If I try to umount /mnt/cdrom, it tells me the device is busy.

This is, of course, not really serious as this is only a test server. And while I bet I can fix the problem by rebooting, I'd like to know my options, were this to happen at work and rebooting was less of an option. Is there another way to kill the process or reset the cd-rom?

Giving back to the community
I am posting two scripts I've written that I find generally useful.

First, "ri" is a very old one which I keep forgetting to work on, but it's operational (however limited). It stands for "replace in", and it's designed to replace words in a bunch of files at a time. Example: ri my_old_website my_new_website *.html

I mean to work more on ri. Read notes on the script if you're curious.

The second script is Mandrake specific. It asks you for CDs 1 through 3, copies them to the hard drive in a configurable location (/install-sources by default) and configures URPMI to use those local copies when installing software. That way you will never be asked for the CDs again. It makes urpmi even more useful because you never have to be in front of the computer to feed it CDs when you add or remove packages.

Download ri here and the Mandrake install sources here. Comments, suggestions, code, etc. welcomed. :)
Looking for useful fstab flags/options for XFS. Suggestions?

It's a 10 GB partion and I built XFS into it with these arguments.

#mkfs.xfs /dev/hdaX -d agcount=3 -l size=32m

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