[NTLUG:Discuss] Dell Server with PERC RAID

Chris Cox cjcox at acm.org
Fri Sep 26 10:08:00 CDT 2003


Cameron, Thomas wrote:
> RAID 0+1 (often called RAID 10) is two RAID 0 arrays which are
 > mirrored (RAID 1).  Gives you the benefit of fast striping
 > plus the fault tolerance of mirroring.  It's just ghastly expensive.

Actually RAID0+1 and RAID10 are radically different things.
http://www.acnc.com/04_01_10.html
http://www.lsilogic.com/products/stor_prod/raid/backgrounder1.html

Low end RAID controllers do 0+1 (it's easier to handle).  RAID 10 is
a highly reliable RAID, RAID 0+1 isn't.  You'll only find RAID 10
on your high end controllers (e.g. a MegaRAID Elite 1600 can do
RAID 10, perhaps a bit old, but works well with Linux).

Since disk has become cheap, creation of RAID 10's is now
quite practical (remember 4G drives used to cost $3000).
On systems where it works right you get the performance of
RAID0 with the reliability of RAID1 AND.. unlike RAID0+1,
you can more than one drive failure (depends on location and
number of columns though).

RAID10 is considered the creme de la creme of RAID (but
probably the most expensive RAID config... but practical
considering today's disk prices).  You may have to pay
to get a controller and setup that supports RAID10 though.

If you need HIGH reliability and FAST reads/writes...
RAID10 might be a viable choice for you.  Most roll
the dice and use good quality SCSI and run RAID0+1
though (mostly because of limitations in their choice
of RAID controller though).  Or run just RAID1 or
run RAID5 (slow writes and slow rebuilds).

The web links above do a pretty good job showing
the differences between the various RAID levels.











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