-----Original Message----- From: Adam Nielsen [mailto:[email protected]] Sent: Sunday, December 06, 2009 7:45 PM To: Larry White Cc: [email protected] Subject: Re: PowerEdge 2900 Onboard SATA API?
>> Is AHCI the common API for communicating to the SATA H/W by most O/S's? Is >> this what Linux uses or is there another API that provides cross platform >> support? >According to Wikipedia AHCI is a hardware independent way of accessing >SATA devices. I know that early SATA interfaces didn't support the AHCI >interface, but I think many recent ones do (certainly all the Intel >chipsets seem to.) I want to say that AHCI wasn't introduced until ICH5 or ICH6, but I'm not totally sure about this. >If you want to support many chipsets with one driver, AHCI would appear >to be the way to go. I have AHCI support compiled into my Linux kernel >running on a PE2950, but it doesn't appear to be in use. I can't >remember whether this is because I have a chipset-specific driver doing >the job instead, or whether I just have no disks plugged into the >onboard controller. So, if there is an on-board SATA I/F and AHCI is not in use, what other cross platform API options are there? >I guess the only way you could know for sure would be to compile a Linux >kernel with *only* the AHCI driver and boot that, and see if it can >detect any of your disks in the boot messages. Yep, this would probably be one way to tell if is supported. Of course, I would hope that if the proper AHCI signature was present in PCI config space, it really should be available. >> The AHCI emulation mode sounds nice since it would allow our >> existing IDE driver to support SATA here with little work. >I believe AHCI itself does not provide legacy emulation, this is a >chipset specific feature. I think most Intel chipsets let you access >the SATA drives as though they were standard IDE devices connected to a >PIIX4 controller, but some other chipsets I have used do not provide >this feature. It sounds like AHCI may be the right way to go for cross platform support. I would certainly hope that any server that has no PATA connection on-board, only SATA, would support AHCI. >I take it running your OS inside a VM is not an option? We started looking at this a while back, but haven't gotten much done as of yet. >And it's high >performance enough that (even though it's circa-1980) using BIOS calls >to access the disk is also out of the question? Absolutely... I would certainly think that using BIOS calls for normal I/O within our O/S would sacrifice considerable performance which we are not prepared to do. >I guess asking your >customers to set the BIOS to legacy mode would at least give you time to >figure out a solution. If this is available, then yes. As I mentioned earlier, our 2900 doesn't seem to have this option in our PE's BIOS, which is why I am wanting to make sure we are headed down the right path with this. Thanks, Larry _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
