SATA ports on the ASUS M4N78 PRO motherboard?

Arno wrote:
Bob Willard wrote:
Daniel Prince wrote:
Arno wrote:

Possibly. But you should not use mainboard RAID anyways. Better
use software RAID or get a separate RAID controller.
How much CPU time does a software RAID consume compared to an
inexpensive separate RAID controller? Or does it not really matter
if you have three or more CPU cores?
--

RAID0 and RAID1 are pretty light users of CPU time, until you
need to rebuild a RAIDset following a HD replacement. RAID5 does
require more computes during writes. So, I'd be willing to
user software RAID for RAID0/1, but I'd think seriously about
hardware for RAID5/6.

RAID5/6 is more I/O intensive. CPU load does not matter even
there, unless your CPU is really, really slow or you have
a RAID6 with 2 drives missing. Just to give you a number,
my old AMD Athlon64 X2 5600+ does 5.2GB/s for an undegraded,
Linux software RAID6. So you need something like 20 current
SSDs in one RAID6 array to saturate one core.

What does matter is that you have a fast datapath to the
controller. PCI-E attached SATA controllers are typically
fine.

Arno

Interesting. Have you measured the CPU overhead caused by
continuous writes to a software-based RAID5/6 RAIDset on
relatively current CPUs? I ask, because I have not had the
opportunity to do so for a few years.
--
Cheers, Bob

Hi!

What types of drives can be used in AHCI mode?

Any serial ATA drive can be used with a host controller operating in AHCI
mode.

The difference is mainly for the software that works with the drive. An
operating system will likely need a driver to recognize the serial ATA
controller when it's running in AHCI or RAID mode.

What types of drives can NOT be used in AHCI mode? Are there any
Windows XP AHCI drivers?

You get the drivers from your hardware, chipset or motherboard manufacturer.
For Windows XP and earlier, you will need to slipstream them (difficult from
what I hear -- never tried it) or have a 3.5" floppy diskette with the
drivers available at setup time.

Does this mean that if you have two drives in a mirrored RAID, you
cannot use any optical drive or any single hard drives on the
motherboard ports? Thank you in advance for all replies.

See your chipset or motherboard maker's documentation for the absolutely
correct (well, hopefully) answer. My experience with real hardware RAID
controllers has shown that you can have optical (and other) drives attached.
However, the "RAID" built into a chipset is not "real" hardware RAID. Still,
CD-ROMs and most other serial ATA drives are probably supported. It's easy
to find out if you have the hardware there, and no harm will come from your
trying it.

The RAID utilities you will have access to should not have a problem
configuring a "container" that has only a single drive in it. However, you
should not be fooled into thinking that this drive will have a standard
format readable from any other serial ATA controller. It probably won't.

William

Bob Willard wrote:
Arno wrote:
[...]
RAID5/6 is more I/O intensive. CPU load does not matter even
there, unless your CPU is really, really slow or you have
a RAID6 with 2 drives missing. Just to give you a number,
my old AMD Athlon64 X2 5600+ does 5.2GB/s for an undegraded,
Linux software RAID6. So you need something like 20 current
SSDs in one RAID6 array to saturate one core.

What does matter is that you have a fast datapath to the
controller. PCI-E attached SATA controllers are typically
fine.

Arno

Interesting. Have you measured the CPU overhead caused by
continuous writes to a software-based RAID5/6 RAIDset on
relatively current CPUs? I ask, because I have not had the
opportunity to do so for a few years.

Sorry, this is just the boot-time benchmark that Linux does.
I do not have a RAID5/6 running at the moment, just RAID1
(one of them 3-way) arrays. But I supect these numbers are
accurate and will give you something like 10% CPU for
continuous writes on a 4 disk RAID6 and maybe around 20%
on a 8 disk one. I may have a chance to run benckarks on
a 8 disk Software RAID6 in the next few days though. Will
post in that case.

Arno
--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

William R. Walsh wrote

What types of drives can be used in AHCI mode?

Any serial ATA drive can be used with a host controller operating in AHCI mode.

The difference is mainly for the software that works with the drive.
An operating system will likely need a driver to recognize the serial
ATA controller when it's running in AHCI or RAID mode.

What types of drives can NOT be used in AHCI mode?
Are there any Windows XP AHCI drivers?

You get the drivers from your hardware, chipset or
motherboard manufacturer. For Windows XP and earlier,
you will need to slipstream them (difficult from what I hear

Nope, very easy.

-- never tried it) or have a 3.5" floppy diskette with the drivers available at setup time.

Does this mean that if you have two drives in a mirrored RAID,
you cannot use any optical drive or any single hard drives on
the motherboard ports? Thank you in advance for all replies.

See your chipset or motherboard maker's documentation for the
absolutely correct (well, hopefully) answer. My experience with real
hardware RAID controllers has shown that you can have optical (and
other) drives attached. However, the "RAID" built into a chipset is
not "real" hardware RAID. Still, CD-ROMs and most other serial
ATA drives are probably supported. It's easy to find out if you have
the hardware there, and no harm will come from your trying it.

The RAID utilities you will have access to should not have a problem
configuring a "container" that has only a single drive in it.
However, you should not be fooled into thinking that this drive will
have a standard format readable from any other serial ATA controller.
It probably won't.