[Sunhelp] SSA 112

[Bjrn Ramqvist]

Lara Matthews wrote:
> 
> Hi All
> 
> Could someone please explain the difference between RAID0+1 and RAID1+0
> or is there an info I could read up about his.

Hi,

The different RAID-levels could be easily explained by these numbers

RAID-0 = pure 'striping', ie spread data across the disks. fast, but
insecure.
RAID-1 = mirroring. two (or more) disks contain the exact same
information. very safe, but expensive.
RAID-3 = striping with parity, mainly for large sequential data
transfers. reasonably safe, reasonably fast.
RAID-5 = striping with parity, mainly for I/O transactions. reasonably
safe, reasonably fast.

RAID-0+1 would mean striping between multiple mirrored disks.
RAID-1+0 is the same, just the other way around. (mirroring between
striped units)

Now, I'm not all that expert on this, but it seems to be logical that
RAID-1+0 would be both fast and reliable, although expensive.

We use hardware-based external RAID-3/5 on our servers. That means if
the sequential throughput goes above a certain limit, the array
automaticly switch over to RAID-3 from RAID-5.


	/Regards, Bjorn