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RE: [linux-lvm] Building up a RAID5 LVM home server (long)



... SNIP ...
> >What if the I broke everything into 10 GB pieces, and 
> created multiple 
> >raid5 sets?  Then I could LVM2 them together and have a large 
> >filesystem that way.
> >
> >a=20GB, b=30GB, c=40GB
> >
> >a-1 + b-1 + c-1 = md0 (approx 30 GB storage)
> >a-2 + b-2 + c-2 = md1 (approx 30 GB storage)
> >      b-3 + c-3 = md2 (waiting for one more drive)
> >            c-4 = md3 (waiting for two more drives)
> >  
> >
> This is sorta what I do.  But in my opinion the gain of having RAID5 
> (over RAID1) is when you get over 3 disks...  at 3 disks you 
> are burning 
> 33% for redudnacy... 25% or 20% or  17% sounds better to me.  
> I guess if 
> you go too far it costs in calculating the parity.

Overhead: Yea, OK. Nothing is without a price.
I fooled around with various ideas, and came up with this for my
particulars:
(Note, rounded to nearest GB)

80 GB	/dev/hda	60 GB /dev/hdb	40 GB	/dev/hdc	45 GB
/dev/hdd

GB		/dev/md0 (RAID0)
40		/dev/hdc
15		/dev/hda1
55		
		
		/dev/md1 (RAID0)
45		/dev/hdd
10		/dev/hda2
55		
		
		/dev/md2 (RAID5)
55		/dev/md0
55		/dev/md1
55		/dev/hda3
55		/dev/hdb
220

Yea, OK, so like the 220 is a bit optimistic, but should get pretty close to
that.

What do you think?



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