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Re: install Etch with raid level 10

On Wed, Sep 26, 2007 at 05:58:14PM +0100, A J Stiles wrote:
> *No* bootloader supports any kind of RAID.  All any bootloader knows how to do 
> is read in the kernel and the initial ramdisk image from contiguous sectors, 
> and start up the kernel.
> However, *if* you ensure that your whole /boot partition fits right within one 
> half-stripe of the RAID0 layer  (i.e. all on the same disk)  then this won't 
> matter  (except you'll have some wasted space on the other disk).  You can 
> easily copy the /boot partition manually to the other device in the RAID1 
> layer, using dd.  The motherboard will always boot from the same drive; then 
> once the kernel is running, the RAID array will be recognised as such and 
> maintained in sync with itself.

You would need huge stripe sizes to fit the kernel and everything else
in it.  A simple raid1 setup works just fine with both grub and lilo and
makes for a nice reliable setup.

> Also, *don't* use a RAID1 for swap space:  it impacts performance with little 
> practical benefit.  Use separate swap partitions from each drive  (just to 
> keep the partitioning schemes the same)  instead.

No.  DO use raid1 for swap.  It has extremely serious impact if a drive
fails.  If you have none raid swap and a drive fails, the system crashes
with likely data loss.  It is not about performance but about
reliability.  It also has no impact on performance.  In fact I run swap
on top of LVM and it doesn't impact performance.  Use swapfiles if you
want (no difference in performance there anymore either).

Where people get the idea that swap dying on you isn't important is
beyond my imagination.

Len Sorensen

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