On Mon, Sep 14, 2009 at 11:42:42AM -0700, James Ward wrote:
> I'm setting up a new BackupPC server as my current one has gotten  
> full.  This system has 2G RAM, quad Intel(R) Xeon(TM) CPU 3.20GHz and  
> a 3ware 6.5T array.  I believe the array is currently RAID5 with no  
> hot spare.  From what I'm reading, RAID5 is a no-no as is ext3?

Others have commented on whether RAID5/6 is OK from a performance POV;
probably everyone will agree that RAID10 is faster than RAID5/6, and
whether you need the extra speed depends on how fast you need it to be.

If you do choose RAID5/6, I worry much more about your survivability in
case of disk failure.  Hint, RAID5 fares much worse than RAID6.
Your lack of a hot spare doesn't help either.

The short version of the story is that with RAID5
1 you lose a disk

2 you go to rebuild from your remaining disks

3 you have a read error on one of your remaining disks
  (pretty darn likely with today's large hard disks)

4 your array is un-rebuildable and you've lost the data contained
  on the raid chunk containing the read error.  

  The good news is that the vast majority of your data is still readable,
  and if you're real lucky, the error will occur in empty space in
  the filesystem

5 BUT...To get your remaining data back onto raid-protected storage you
  probably have to copy it to a newly built array.  

the articles below discuss this in great detail.  He talks about RAIDz
and RAIDz2; for these purposes, RAIDz is basically equivalent to RAID5
and RAIDz2 is basically equivalent to RAID6.   

  http://blogs.sun.com/relling/entry/raid_recommendations_space_vs_mttdl
  http://blogs.sun.com/relling/entry/zfs_raid_recommendations_space_vs
  http://blogs.sun.com/relling/entry/a_story_of_two_mttdl


One thing you can do to help prevent this kind of thing is to make sure to
scrub your RAID frequently.  Not sure how to do that with your 3ware but i'm
sure it's possible.

danno
--
Dan Pritts, Sr. Systems Engineer
Internet2
office: +1-734-352-4953 | mobile: +1-734-834-7224

Fall 2009 Internet2 Member Meeting, October 5-8
Hosted by the University of Texas at San Antonio and LEARN
http://events.internet2.edu/2009/fall-mm/

------------------------------------------------------------------------------
Come build with us! The BlackBerry® Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay 
ahead of the curve. Join us from November 9-12, 2009. Register now!
http://p.sf.net/sfu/devconf
_______________________________________________
BackupPC-users mailing list
BackupPC-users AT lists.sourceforge DOT net
List:    https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki:    http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/