HostRaid support on FreeBSD

[Scott Long]

Maxim Sobolev wrote:
> Actually support for all those ATA/SCSI software RAIDs, as well as 
> Vinum, should be collapsed into a set of GEOM modules. And no, I am not 
> volunteering. ;)

While a lot of good work is going into GEOM modules right now, there are
two fundamental problems there:

1) lack of unified device/array metadata management.
2) lack of unified error recovery and spare assigment.

Many of the metadata designs in use are rather complex and require a
unified view of the system in order to assure consistency and
correctness.  The current stand-alone GEOM modules that exist or are in
development have no concept of this.  GEOM really doesn't provide any
type of a framework to give this consistency either.

The easy part of RAID is the mirror/stripe/parity transforms.  The hard
part of RAID is the error recovery and configuration algorithms.  They
are also the most important since they directly affect the reliability
of the subsystem.  GEOM is a great framework for prototyping block level
transforms, but the lack of infrastructure for the other pieces really
does make it a less-than-ideal solution.  At this point, all it really
allows is an easy way to mimic ccd(4) (although it would be quite
interesting to implement block-level snapshots and possibly volume
management with it).

> 
> Vinum work is under way, as long as I know, it should not be too hard to 
> add appropriate code to read RAID configuration not from disk, but from 
> appropriate ATA or SCSI controller.

I have absolutely no idea what you are talking about here.  Modern RAID
controllers, and _especially_ software raid controllers, do not store
their configuratin data in hardware.  There are a few exceptions where
it is stored and kept private to the hardware for sanity-checking
purposes, but it is not exposed to the OS.

Scott
> 
> -Maxim
> 
> Eric Veraart wrote:
> 
>> Hello,
>>
>> I was browsing through the mailinglist and was wondering on what the 
>> status was on HostRaid support on FreeBSD. Certainly since the new 
>> Intel Pentium 4 Entry Server Board SE7210TP1-E supports HostRaid and 
>> we're planning to use those boards. The SCSI version of the board has 
>> an Adaptec AIC-7901 chip and the SATA version has a 6300esb chip. I 
>> can find Linux drivers, but development for FreeBSD seems to be lying 
>> still.
>>
>> So who is working on it, or who doesn't have the time/resources to do 
>> this?
>>
>> Greetings,
>> Eric
>>
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> 
> 
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