Re: [gentoo-server] RAID0 sw on top of RAID1 sw or RAID1 on top of RAID0

[Andrea Ferraris]

> Other way around.  A stripe set of 2, 2disk mirrors is the winner, but I

Sorry I have some problems with the language (I'm not a native speaker,
neither well understander ;-) 
Is it raid0 on top of 2 raid1? 

> don't know how to do this in software w/ the md driver for instance.

I don't remember the details of the syntax of my raidtab, 
but I did it, something like that:

raiddevice /dev/md1
raidlevel    1
chunksize 8
/dev/sdb2  raiddisk 0
/dev/sdc2  raiddisk 1

raiddevice /dev/md2
raidlevel    1
chunksize 8
/dev/sdd2  raiddisk 0
/dev/sde2  raiddisk 1

raiddevice /dev/md3
raidlevel    0
chunksize 16
/dev/md1 raiddisk 0
/dev/md2 raiddisk 0

/dev/sdb2, /dev/sdc2, /dev/sdd2 and /dev/sde2 are all
about 500 MB.

then 

# mkraid /dev/md1
# mkraid /dev/md2
# mkraid /dev/md3

# mkswap /dev/md3
# swapon /dev/md3

then I had to take out from /etc/fstab the 
swap, due to an error at boot that sent me
to single user mode. Maybe because /dev/md1
and /dev/md2 couldn't be marked by fdisk as 
raid autodecect partitions (0xfd). Now I activate the
swap from an init script (with /sbin/swapon /dev/md3)
and all is working well.

I couldn't find detailed explanation or examples for the 
chunksize.
Do you know wich one have had been the best for
my setup?

> With raid10 you can lose two disks off different channels and still have
> your data.
>
> Matt
>
> Andrea Ferraris wrote:
>
> > What do you suggest?
> >
> > I made the swap (about 1 GB) of my new gentoo 1.4 server
> > (512 MB RAM) on a RAID0 sw of 2 RAID1 sw, but now
> > I was wandering if it isn't better to do a RAID1 on top of
> > 2 RAID0 or if it's the same for performance and reliability.
> >
> > Regards,
> >                     Andrea