[Novalug] raid mirror

[Aaron Porter]

On Wed, Jul 29, 2009 at 3:03 PM, Bryan Seitz<seitz at bsd-unix.net> wrote:
> Any mismatches can cause various issues from data corruption to data loss to bad performance.

This is just plain FUD.

I work with hundreds of RAID groups, multiple thousands of spindles.
Some of the systems are nearly 5 years old now. You just don't find a
reliable vendor with a supply of 400gb SATA1 disks these days, or
160gb ATA, etc so you mix and match with what's available for
purchase. Nearly any RAID system (3ware, Areca, LSI, Adaptec, Dell
PERC, Infortrend, Nexsan, Storagetek, Linux MD, EVMS, the list is
long) will happily chew up mismatched disks. In the hardware based
configs you'll probably waste some usable disk; most software raid
won't even hit you with that. Your performance in many cases will be
restricted by your slowest spindle but for MANY applications that's
just not a concern. I'd avoid pairing a shiny new Velociraptor with a
5 year old 300gb SATA1 disk since it'd be a waste of money, but I'd
certainly expect it to work just fine if I tried it.

> In the case of 7200 vs 5400 I would imagine reads would be faster than 1 drive itself but writes
> would only be as fast as the 5400RPM drive, as RAID1 has to verify data has been written to each
> mirror.

True, but if protection against single disk failure is the goal and
5400 rpm is fast enough for the application you're still golden.

> With drives being so cheap these days, you would be better off springing for a new matching set :)

Just how much Seagate stock do you own? The I in RAID is for
inexpensive. Embrace it.