Ron Johnson wrote:
On Tue, 2003-09-02 at 11:14, Andrew Sullivan wrote:

On Thu, Aug 28, 2003 at 03:26:14PM -0600, scott.marlowe wrote:

My experience has been that once you get past 6 disks, RAID5 is faster than RAID1+0.

Also depends on your filesystem and volume manager. As near as I can tell, you do _not_ want to use RAID 5 with Veritas.

Why should Veritas care?  Or is it that Veritas has a high overhead
of small block writes?

I agree with Scott however only when it's hardware RAID 5 and only
certain hardware implementations of it.  A Sun A1000 RAID 5 is not
equal to a Sun T3.  Putting disk technologies aside, the A1000 array
XOR function is in software whereas the T3 is implemented in hardware.
Additionally, most external hardware based RAID systems have some
form of battery backup to ensure all data is written.

Veritas Volume Manager and even Linux, HP-UX and AIX LVM works just
fine when slicing & dicing but not for stitching LUN's together.  IMHO,
if you have the $$ for VxVM buy a hardware based RAID solution as well
and let it do the work.


Greg Spiegelberg
 Sr. Product Development Engineer
 Cranel, Incorporated.
 Phone: 614.318.4314
 Fax:   614.431.8388
Cranel. Technology. Integrity. Focus.

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