Re: HostRaid support on FreeBSD

Scott Long wrote:

> 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.

Well, my knowelege about internals of software RAID controllers is quite 
limited, but as long as I know they are no more than BIOS with UI for 
setting up RAIDs and interface to main BIOS that hides internal RAID 
structure allowing to boot off the RAID. Also they provide some 
persistent storage for RAID configuration, I assume either in some 
controller's NVRAM or on the HDDs. Therefore, the same set of GEOM RAID 
modules can work with different software RAID controllers (SCSI, ATA, 
SATA etc) if there will be a standard way to extract this info from the 
controller's driver, and present it in some common format. That's what I 
am talking about.

-Maxim

> 
> 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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> 
> 
> 
>