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On Thu, Feb 16, 2006 at 02:13:55PM -0500, Webmaster@xxxxxxxxxxxxxxxxxxx wrote:
>In the book, he uses a NAS box to handle the MYSQL and FS. I just don't
>like the idea of using a single box. Isn't there anyway you can utilize
>each hard drive on each real server node, kind of like a virtual raid array?
Here are some questions to ask to compare which avenue you would like to
take:
1) In a cluster filesystem, how many real servers can go down at one time
and leave the virtual raid array still operational?
2) In a NAS box, how many drives can die simultaneously and the system is
still operational?
3) In a cluster filesystem, what happens if half of the switch ports
just all of a sudden die, or the whole switch, or some corruption
happens in your switch and several ports suddently segment themselves
into its own VLAN?
4) For a NAS box, ask #3. (Hint: a good NAS like the FAS270c with twin
heads will do a complete takeover if necessary, so 3 of the 4 ethernet
ports can lose connectivity. As long as one is still connected, that
one head can serve the load of both heads.)
5) In an NAS box, does it have multiple power supplies? Multiple
ethernet ports? Multiple parity drives? Multiple spare drives?
6) How much money do you have available to spend? Are you counting the
amount of time it will take you to keep a cluster filesystem running and
stable as compared to the relatively troublefree NAS boxes (assuming you
don't undersize it)?
In terms of complete disaster recovery:
7) How long does it take to backup a complete cluster fs?
8) How long does it take to backup a NAS?
9) How long would it take to rebuild and restore a cluster if half of
the machines died all at once? If all of the machines died at once?
10) How long would it take to rebuild and restore a NAS box if half of
the drives died all at once? If all of the drives died at once? If
both power supplies died at the same time?
If you think that you'll never see any of these situations, you might be
lucky and never will, but my general experience with computer hardware
is that things run very smooth for a very long time, and then something
hiccups hard and takes a bit of work to recover from. I've also heard
mention that "Murphy was an optimist." :-)
If you can't tell, I'm of the opinion that a NAS will do more for you
than a cluster filesystem, but keep in mind that's also my comfort zone.
If I was daily into the inner workings of a cluster fs production
system, I might feel differently.
--
Regards... Todd
OS X: We've been fighting the "It's a mac" syndrome with upper management
for years now. Lately we've taken to just referring to new mac
installations as "Unix" installations when presenting proposals and
updates. For some reason, they have no problem with that. -- /.
Linux kernel 2.6.12-15mdksmp 2 users, load average: 0.40, 0.27, 0.15
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