Software RAID5

[Gabriel Dragffy]

On 22 Sep 2007, at 01:13, Maxim Khitrov wrote:
>
> However, a simple solution to that is to get a 64+ MB USB flash drive
> and put the kernel on that. Just use fdisk and bsdlabel to write the
> boot blocks. As long as the kernel has all needed drivers and you
> specify which root device to use (either via kernel configuration or
> /etc/fstab), that should allow you to put everything else on the RAID
> array. This is how I currently do full-disk encryption on my laptop
> using GELI. Kernel is outside, everything else is encrypted, same idea
> for RAID.
>
> I haven't ever done software RAID in FreeBSD, so can't help you with
> the practical aspects of it. But I will say that technical or not, man
> pages are still the best way to learn about these things. From what I
> can see, RAID 5 is done through vinum, and GEOM offers RAID 3. Someone
> else here may be able to tell you which one is better to use.
>
> It's also worth noting that with software, the performance of RAID 5
> is not going to be very good. I generally advise against software RAID
> 5. If you want good performance and reliability using software RAID,
> the best bet is RAID 10, but there the utilization is 50%. I think
> that if you can afford another 500GB drive and performance is
> important to you, a software RAID 10 using GEOM will perform much
> better. It is also easier to recover, and you can lose two drives (not
> any two, but still) without completely losing all the data.
>

Hi, thank you for your post. I read the following in the BSD handbook  
which lead me to believe I could have root on RADI5:

<quote>
There is another option as well, to have /boot/loader (Section  
12.3.3) load the vinum kernel module early, before starting the  
kernel. This can be accomplished by putting the line:
geom_vinum_load="YES"
into the file /boot/loader.conf.
</quote>

That's here: http://www.freebsd.org/doc/en_US.ISO8859-1/books/ 
handbook/vinum-root.html

I appreciate your post about using an alternative system to RAID 5.

Many thanks

Gabriel