Softraid controllers and Linux

Softraid controllers and Linux

[Jim Klimov]

Hello linux-raid,

  I have tried several cheap RAID controllers recently (namely,
  VIA VT6421, Intel 6300ESB and Adaptec/Marvell 885X6081).
  
  VIA one is a PCI card, the second two are built in a Supermicro
  motherboard (E7520/X6DHT-G).

  The intent was to let the BIOS of the controllers make a RAID1
  mirror of two disks independently of an OS to make redundant
  multi-OS booting transparent. While DOS and Windows saw their
  mirrors as a singular block device, Linux (FC5) accessed the
  two drives separately on all adapters.

  Is this a bug or a feature of the kernel driver support? (I did
  not try vendors' binary drivers, if there are any).

-- 
Best regards,
 Jim Klimov                          mailto:klimov@2ka.mipt.ru

Re: Softraid controllers and Linux

[Jeff Garzik]

Jim Klimov wrote:
> Hello linux-raid,
> 
>   I have tried several cheap RAID controllers recently (namely,
>   VIA VT6421, Intel 6300ESB and Adaptec/Marvell 885X6081).
>   
>   VIA one is a PCI card, the second two are built in a Supermicro
>   motherboard (E7520/X6DHT-G).
> 
>   The intent was to let the BIOS of the controllers make a RAID1
>   mirror of two disks independently of an OS to make redundant
>   multi-OS booting transparent. While DOS and Windows saw their
>   mirrors as a singular block device, Linux (FC5) accessed the
>   two drives separately on all adapters.

You did not buy a RAID controller.

http://linux-ata.org/faq-sata-raid.html

If you really want to use proprietary RAID on Linux, you may use dmraid, 
but using MD for software RAID is much more robust.

	Jeff

Re: Softraid controllers and Linux

[Bill Davidsen]

Jim Klimov wrote:

>Hello linux-raid,
>
>  I have tried several cheap RAID controllers recently (namely,
>  VIA VT6421, Intel 6300ESB and Adaptec/Marvell 885X6081).
>  
>  VIA one is a PCI card, the second two are built in a Supermicro
>  motherboard (E7520/X6DHT-G).
>
>  The intent was to let the BIOS of the controllers make a RAID1
>  mirror of two disks independently of an OS to make redundant
>  multi-OS booting transparent. While DOS and Windows saw their
>  mirrors as a singular block device, Linux (FC5) accessed the
>  two drives separately on all adapters.
>
>  Is this a bug or a feature of the kernel driver support? (I did
>  not try vendors' binary drivers, if there are any).
>
>  
>
If I understand how Linux uses the drives, you have to make them raid 
manually. However, the nice thing about BIOS RAID is that it will boot 
the system if the first boot drive fails. If the drive fails hard the 
BIOS will go to the first functional drive and boot. But if you get a 
CRC error, some BIOS will try another and some will just fail.

Vendor dependent.

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

SATA ontrollers and Linux MD

[Ruth Ivimey-Cook]

 Hi,

I've a file server running on an Athlon XP 3200+ motherboard, currently using a
mixture of PATA and SATA-150 drives and Fedora Core 5 Linux. 5x 120GB Seagate
drives form a single raid-5 volume. One of those drives has failed, the rest
are old, and I'm looking to replace all of them. I'd appreciate any help
selecting components!

The motherboard uses a KT600 chipset and so includes two SATA-150 connections
serving 2 of the Raid-5 disks. The rest of the Raid-5 is currently run off a 2
channel Highpoint PATA PCI controller.

Currently, I'm looking at buying 5 Samsung P120 series drives - the 250GB
SATA-300 "SP2504C". To reduce cost I might possibly use 4 rather than 5, or
might go for the 160GB variant. Reason for these drives is I've found them
quiet, and reasonably fast & cool - all important to me. I don't need
cutting-edge performance, but reliability is good!

Controller-wise, finding suitable SATA-300 controllers is hard. Requirements
include at least 4 internal ports and a PCI not PCIe interface. I might end up
with a SATA-150 controller and upgrade it and the MB sometime later. I'm not
really after a dedicated RAID controller such as the 3ware ones, as (a) I can't
really justify the cost and (b) I want to use Linux MD for reasons of
portability.

Aside: Over PCI, is it better to use two separate 2-channel PCI cards or one
4-channel card? For example, 2x Sil 3112 chips or 1x Sil 3114, given that
you're using all disks in JBOD mode?

I'm very tempted by the Sil 3124 controller, although I've not had much luck
finding a PCI version of it. In the States there's a company "SATACard" who
appear to make one that's suitable, but I can't find a UK supplier. Scan are
selling the Supermicro 8 Port SATA 2 RAID Card AOC-SAT2-MV8, but with not much
info other than it's based on the Marvell Hercules-2 Rev. C0 SATA host
controller. Others that include the various Promise and Highpoint controllers,
but my experience of Promise QA is not good, and Highpoint SATA-300 seems to
use Infiniband, for which Linux support looks really cutting edge. I don't want
to use proprietary drivers and I'd much prefer something FC5 supports natively.

Any thoughts?

Thanks,

Ruth