atacontrol software or hardware raid

[Josh Paetzel]

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Omer Faruk Sen wrote:
> How can I detect if system has Software or hardware raid? Since in manual page:
> 
>  The atacontrol command can also be used to create purely software RAID
>      arrays in systems that do NOT have a "real" hardware RAID card such as a
>      Highpoint or Promise card.  A common scenario is a 1U server such as the
>      HP DL320 G4 or G5.  These servers contain a SATA controller that has 2
>      channels that can contain 2 disks per channel, but the servers are wired
>      to only place a single SATA drive on each channel.
> 
> Or how can I find out if the hardware is "real" hardware RAID card?
> For example my system has following dmesg output:
> 
> ad4: 152627MB <Seagate ST3160815AS 4.AAB> at ata2-master SATA300
> ad6: 152627MB <Seagate ST3160815AS 4.AAB> at ata3-master SATA300
> ar0: 152625MB <Intel MatrixRAID RAID1> status: READY
> ar0: disk0 READY (master) using ad6 at ata3-master
> ar0: disk1 READY (mirror) using ad4 at ata2-master
> 
> This system is an intel server with S3210SH server board in it. While
> installing system I see ad4,ad6 and ar0 as harddrives in sysinstall. I
> choose to install ar0.
> 
> Additionally as far as I see ar0 is very susceptible to errors since a
> single CRC error can break the RAID consistency is that normal?  I
> really appreciate those who uses such a kind of RAID1
> 
> Regards.
> _______________________________________________
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ar RAID devices are almost always software/BIOS RAID.  In this case
intel matrix raid is software RAID provided by the system BIOS.  The
disadvantages of using it is your RAID array isn't portable to machines
that don't have the same BIOS raid implimentation.

One of the advantages of BIOS RAID is that you can boot from stripes,
which you aren't doing anyways.

You'll probably find that disabling the motherboard RAID and creating a
gmirror device is a better option for software RAID 1.

- --
Thanks,

Josh Paetzel

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