[SATLUG] Re: now help with raid setup on linuxmce box

Todd W. Bucy toddwbucy at grandecom.net
Tue Sep 23 10:04:32 CDT 2008


On Tue, 2008-09-23 at 09:46 -0500, John Pappas wrote:
> On Tue, Sep 23, 2008 at 07:14, Todd W. Bucy <toddwbucy at grandecom.net> wrote:
> 
> > On Mon, 2008-09-22 at 17:58 -0500, John Pappas wrote:
> > > On Mon, Sep 22, 2008 at 13:11, Todd W. Bucy <toddwbucy at grandecom.net>
> > wrote:
> > > >
> > > > In this particular box I will have 2 320 gig and 2 500 gig drives.
> >  with my
> > > > raid I want it all redundancy, as much
> > > > space as possible and speed.
> > >
> > > How does this sound:  Partition up the 500GB disks like so:
> > > SDx1 = 128MB RAID (Linux fd = raid autodetect) Bootable
> > > SDx2 = 6GB RAID (linux fd)
> > > SDx3 = ~174GB RAID (linux fd)
> > > SDx4 = 320GB RAID (linux fd)
> > >
> > <<SNIP>
> > >
> >
> > I thought of something like this but was warry.  I seem to remember a
> > discussion on this topic a while back that trongly discouraged setting
> > up multiple raids on the same drives.  Are there any particular worries
> > that I need be aware of?
> 
> 
> If this were a server hosting more than a household, "best practice" would
> suggest to split RAID types on different raidsets, and there would be $$ to
> support it.  In this case, the I/O loads are not going to be such that it
> will matter.  With another drive (a 500 probably) you could do a RAID 5, get
> 1TB and have 33% overhead, and use the 320's for the OS mirror
> 
> 
> > I know that if I have a failure of one of the 500 GB drives getting it
> > replaced will be real complicated.  Are there
> > strategies for addressing this now so as to make my life easier then?
> 
> 
> In that case, you simply replace, repartition the replacement (Use the good
> one to match partitioning) and run a couple commands (maybe not at the same
> time, as the multiple rebuilds are I/O heavy).  You may have to manually
> fail the partitions, but in the case of a real failure, that will be usually
> taken care of by the system, so all of them will be 1/2 or 3/4, so you will
> need to run the following to add the replacements and initiate rebuild:
> `mdadm /dev/md0 -a /dev/sdx1`
> `mdadm /dev/md1 -a /dev/sdx2`
> `mdadm /dev/md2 -a /dev/sdx3`
> `mdadm /dev/md3 -a /dev/sdx4`
> Run `cat /proc/mdstat` to monitor progress.
> 
> Not too hard, right?
> 
> HTH,
> jp

thanks alot, I will file this email in my emergency folder for future
reference. 

Thanks 
Todd



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