Re: Raid: software or hardware



Hello

I have mainboard: gigabyte P965S3.
I have 2 SATA interfaces using builtin Jmicron controller
(and another 4 SATA interfaces)
I upgraded bios to version F12.
I want to make mirror raid.

What's better to use: software or hardware(jmicron)?

Hardware RAID is always preferable over software RAID *if* it is available.
However, I sincerely doubt that the onboard SATA RAID of your motherboard
will be a hardware RAID.

Most likely, it'll be a hardware-assisted software RAID, or if you will, a
"WinRAID", just like a Winmodem isn't a real modem.

1. Using hardware, jmicron (creating raid from bios).
Will gentoo see it ? Is it stable ?

I do not know the JMicron, but true hardware SATA RAID from a chip on the
motherboard is extremely rare and would also make the board more expensive
than its peers.

Even if you enable the RAID functionality of an SATA onboard
hardware-assisted software RAID, this will only be seen as a RAID by
Windows, and then will require you to load the appropriate driver for it,
if Windows doesn't have a driver for it by itself.

In GNU/Linux, such a device is seen as a simple SATA controller, regardless
of whether the RAID functionality is enabled or not, because basically
that's what it is.

If one disk fails how will i know ?

Both true hardware RAID and software RAID would report this via /syslogd,/
or possibly via an additional daemon like Adaptec's Storage Manager for
Adaptec RAID adapters.

Will there be no problem with replacing bad disk with new one ?

The replacement of a failed drive in a RAID array is always subject to
certain delays and restrictions. Not all RAID adapters (or hard disks!)
support hotplugging.

When a drive has been replaced, most hardware RAID adapters will
automatically rebuild the array - which takes some time and will slow down
the machine's performance somewhat - but in software RAID, I believe you
have to rebuild the array manually using /mdadm./



thanx for this info. That's true - jmicron is not real hardware RAID.
Linux kernel has drivers for jmicron software/hardware RAID.

So - what is better ?
1. fully software RAID based on mdadm tool
2. or software/hardware jmicron RAID ?

What would you suggest ?
What is faster ? What makes CPU works less ?
Which solution is more reliable ?

Thanx
.

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