[CentOS] RAID 10 on Install?

nate centos at linuxpowered.net
Sat Oct 31 00:18:02 UTC 2009


ML wrote:
> Hi All,
>
> How can I RAID 10 on install? (the names myRAID1 and myRAID2 are just
> for example purposes)

3rd time this question has been asked in the past few weeks, I believe
the answer is not using the normal installer. I believe if you make
a custom installer with the right modules you can do it by hand in
the console before the installer loads.

Another way which I've suggested and should work is use LVM to
do the striping between two RAID 1 volumes, certainly not as "clean"
as a real RAID 1+0, but you should be able to do it from the
regular installer.

The best way is probably to use a hardware controller.

> What is the rule of thumb for Swap these days. Back a long time ago it
> was double the RAM in the machine.....but that was a long time ago,
> what is best now?

Depends on your needs, I generally use 1GB of swap for most systems that
have up to 4GB of ram, beyond that I use 4GB of swap for most everything
else.

I do have nagios checks that will alert if the system has more than
10% of swap in use.

In my opinion swap is an emergency resource only, the performance
hit is so huge that if your actively swapping 4GB your system is
going to be in an unusable state.

For all of my physical systems I also set /proc/sys/vm/swappiness to
0 to reduce the likely hood of the system going into swap. Virtual
systems running in VMware at least are more likely to go into
swap because of memory ballooning so I don't adjust the swappiness
setting on them away from the default.

nate




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