Comments for Linux ATA RAID HOWTO

17 Jan 2003 13:47 murty

Re: Quasi-hardware raid?
SORRY FOR THE TYPO. This is the corrected sentence:

In the case of MD, the boot partition ( /boot or /) must be either simple non-raid partition or mirror partition but not RAID 0, RAID 5, etc.

> Correct. There is really no hardware
> support other than boot-time help from
> the BIOS on the Promise RAID card (or
> on-board chip). This is because the card
> is actually an IDE port extension card
> with a special BIOS...not really a RAID
> controller card.
>
> ataraid is new but stable, md raid is
> not new and proven to be reliable. MD
> raid has features such as automatic
> repair (syncing), hot spare partition
> and ability to function if one of the
> disks participating in mirror damages.
> ATARAID currently does not have these
> features.
>
> On the other hand, ataraid is friendly
> and seemless with other operating
> systems. Can co-exist with Windows etc.
> Also, gives you the ability to share
> files between operating systems. And
> because ataraid gets help from BIOS, you
> can have any type of raid unlike MD. In
> the case of MD, the boot partition (
> /boot or /) must be either simple
> non-raid partition or mirror partition
> but not RAID 1, RAID 5, etc.
>
> As ataraid development progresses,
> hopefully in future benefits of both
> types of raid will be merged and offered
> to linux users. If you dont want MD raid
> features i.e. want something that
> behaves like hardware raid but you cant
> afford a hardware raid card, you should
> use ataraid.
>

17 Jan 2003 13:44 murty

Re: Quasi-hardware raid?
Correct. There is really no hardware support other than boot-time help from the BIOS on the Promise RAID card (or on-board chip). This is because the card is actually an IDE port extension card with a special BIOS...not really a RAID controller card.

ataraid is new but stable, md raid is not new and proven to be reliable. MD raid has features such as automatic repair (syncing), hot spare partition and ability to function if one of the disks participating in mirror damages. ATARAID currently does not have these features.

On the other hand, ataraid is friendly and seemless with other operating systems. Can co-exist with Windows etc. Also, gives you the ability to share files between operating systems. And because ataraid gets help from BIOS, you can have any type of raid unlike MD. In the case of MD, the boot partition ( /boot or /) must be either simple non-raid partition or mirror partition but not RAID 1, RAID 5, etc.

As ataraid development progresses, hopefully in future benefits of both types of raid will be merged and offered to linux users. If you dont want MD raid features i.e. want something that behaves like hardware raid but you cant afford a hardware raid card, you should use ataraid.

> Hi,
>
> thank You for Your answer. Things are
> quite clear now ;)
>
> As I am curious, there are two more
> questions:
>
> Is there really no hardware support for
> reading, writing
> and repairing the RAID in pseudo
> hardware controllers?
>
> What are the missing functions of
> ATARAID compaired to
> MD raid? (The latter is just software
> raid, right?)
>
> Greetings,
>
> Hans
> P.S.:
> With this background information, is
> there any reason to use
> ataraid instead of md raid?


13 Jan 2003 23:49 hansU

Re: Quasi-hardware raid?

> Hi
> Yes, the real RAID is done in drivers.
> Therefore its Software RAID. However,
> ATARAID is different in the following
> two ways compared to MD Software RAID.
> Otherwise, both are same.
>
> 1. ATARAID takes help from BIOS to read
> disk info and boot
> 2. ATARAID drivers do not have all the
> features of MD RAID


Hi,

thank You for Your answer. Things are quite clear now ;)

As I am curious, there are two more questions:

Is there really no hardware support for reading, writing
and repairing the RAID in pseudo hardware controllers?

What are the missing functions of ATARAID compaired to
MD raid? (The latter is just software raid, right?)

Greetings,

Hans
P.S.:
With this background information, is there any reason to use
ataraid instead of md raid?

13 Jan 2003 06:51 murty

Re: Quasi-hardware raid?
Hi
Yes, the real RAID is done in drivers. Therefore its Software RAID. However, ATARAID is different in the following two ways compared to MD Software RAID. Otherwise, both are same.

1. ATARAID takes help from BIOS to read disk info and boot
2. ATARAID drivers do not have all the features of MD RAID

Because ATARAID is software raid with some help from RAID Card BIOS hardware, its Quasi- or Pseudo hardware. Promise Technology and their vendors would like to tell general public that it IS hardware raid.


> Hello,
>
> does quasi-hardware mean that this kind
> of raid
> controllers are just simle IDE
> controllers and the
> real RAID functionality is done by the
> drivers?
>
> Slightly confused,
>
> Hans


08 Jan 2003 07:29 hansU

Quasi-hardware raid?
Hello,

does quasi-hardware mean that this kind of raid
controllers are just simle IDE controllers and the
real RAID functionality is done by the drivers?

Slightly confused,

Hans

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