How many RAID arrays on a single controller?

  • Thread starter Thread starter Marco De Vitis
  • Start date Start date
M

Marco De Vitis

Hi,
I feel it might be a stupid question, but... do all RAID controllers
only handle a single array?
Say, for example, that you need to build a 4-disk RAID 5 array and a
4-disk RAID 0 array, both on the same machine working simultaneously; do
you necessarily have to use TWO separate controllers (offering at least
4 ports each), or are there 8-port controllers which can handle both
arrays at the same time "separating" somehow their ports into two
different sets?

Thanks.

PS: I'm particularly interested in SATA RAID controllers, but I believe
my question is more generic anyway.
 
Previously Marco De Vitis said:
Hi,
I feel it might be a stupid question, but... do all RAID controllers
only handle a single array?
Say, for example, that you need to build a 4-disk RAID 5 array and a
4-disk RAID 0 array, both on the same machine working simultaneously; do
you necessarily have to use TWO separate controllers (offering at least
4 ports each), or are there 8-port controllers which can handle both
arrays at the same time "separating" somehow their ports into two
different sets?

PS: I'm particularly interested in SATA RAID controllers, but I believe
my question is more generic anyway.
Click to expand...

I believe you have to go into the more expensive ranges to get
a multi-array capability. Or use software-RAID.

Arno
 
Hi,
I feel it might be a stupid question, but... do all RAID controllers
only handle a single array?
No

Say, for example, that you need to build a 4-disk RAID 5 array and a
4-disk RAID 0 array, both on the same machine working simultaneously; do
you necessarily have to use TWO separate controllers (offering at least
4 ports each),
No

or are there 8-port controllers which can handle both
arrays at the same time "separating" somehow their ports into two
different sets?
Yes.

Thanks.

PS: I'm particularly interested in SATA RAID controllers, but I believe
my question is more generic anyway.
Click to expand...

Different controllers have different capabilities. Read the manual of
whatever prospective card you are looking to purchase. IIRC even
cheap Hostraid cards & ROMB can do this so big bucks are not a
requirement.
 
Yes.
Click to expand...

Also often controllers can separate pieces of the disks to make more
than 1 array which is maximally limited by the smallest disk.

So for example if you have 4 drives you could make a raid 1 with 2
disks and 2 disk raid0 with the other two. Additionally if you have 2
100 gig drives you could make a raid 1 with the first 50 gigs of each
drive and a raid 0 with the later 50 gigs (although usually not the
smartest move). There are no hard & fast rules on how you can chop
them up, percentage wise, except that if you have say a 100 gig & 200
gig drive an array can't use more than 100 gigs of each drive.
 
Marco De Vitis said:
Hi,
I feel it might be a stupid question, but...
Click to expand...
do all RAID controllers only handle a single array?
Nope.

Say, for example, that you need to build a 4-disk RAID 5 array and a
4-disk RAID 0 array, both on the same machine working simultaneously;
Click to expand...
do you necessarily have to use TWO separate controllers (offering at
least 4 ports each),
Nope.

or are there 8-port controllers which can handle both arrays at the
same time "separating" somehow their ports into two different sets?
Click to expand...

Why would they have to seperate their ports. They are already seperate
from a logical viewpoint. Arrays are defined by firmware (ie software)
and it is the firmware that decides what ports to use. What is possible
or not is decided by the firmware, not the IDE chips and/or how many
ports or channels they have.

Some brands will support two (or more) identical controllers, the bios
utility just executed once, covering all the controllers as if they were
one card.
 
In Folkert Rienstra typed:
In other words, you don't have a clue, as always.
If you want to believe, go to a church.
Click to expand...
Hi Folkert,
and what has this to do with objective statements?
If You want to discuss on "church" then select another NG!
Horst
 
Previously Horst Franke said:
In Folkert Rienstra typed:
Click to expand...
Hi Folkert,
and what has this to do with objective statements?
If You want to discuss on "church" then select another NG!
Horst
Click to expand...

Oh, that is just Folkert trying to convince people that I am
clueless.

Arno
 
Marco said:
Hi,
I feel it might be a stupid question, but... do all RAID controllers
only handle a single array?
Say, for example, that you need to build a 4-disk RAID 5 array and a
4-disk RAID 0 array, both on the same machine working simultaneously; do
you necessarily have to use TWO separate controllers (offering at least
4 ports each), or are there 8-port controllers which can handle both
arrays at the same time "separating" somehow their ports into two
different sets?

Thanks.

PS: I'm particularly interested in SATA RAID controllers, but I believe
my question is more generic anyway.
Click to expand...

Marco,


Simple answer - yes, you *can* quite simply have two or even three or
more raid arrays on the same hardware RAID controller. Each array will
show up as its own, discrete drive, which in turn can then be
partitioned to your heart's content.

I have an Areca PCI Express controller with 8 ports, and I regularly run
three separate RAID arrays off it. I also have a cheapo Adaptec
controller that does the same.

It's not a stupid question, although daresay I question the relevance of
some of the answers given.


Odie
 
Marco De Vitis said:
Hi,
I feel it might be a stupid question, but... do all RAID controllers
only handle a single array?
Click to expand...

I have several MegaRAID controllers. They have three channels
of {up to...} 15 drives each. You can have multiple RAID0, 1,
and/or 5 arrays built from those 45 drives....
 
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