Date: Thu, 8 Nov 2007 07:18:02 -0800 (PST) From: Doug Ambrisko <ambrisko@ambrisko.com> To: Scott Long <scottl@samsco.org> Cc: freebsd-scsi@freebsd.org Subject: Re: MFI and passthrough Message-ID: <200711081518.lA8FI2O2057303@ambrisko.com> In-Reply-To: <4732C443.1070100@samsco.org>
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Scott Long writes: | Borja Marcos wrote: | > On Nov 6, 2007, at 4:02 PM, Scott Long wrote: | > | >> Doug Ambrisko wrote: | >>> BTW, it works great in this mode if you know what you are doing :-) | >> | >> Can you explain what that means? I recommend against it because it's | >> not a well-tested configuration either in FreeBSD or in Dell. It's not | >> clear, at least to me, how basic things like i/o errors get handled; | >> does SCSI sense data get consumed by the controller firmware, or is it | >> passed through to the OS without problem? | > | > Aha, I see. I assumed that the controller would pass the sense data, | > etc, without problems. | > | >>> | I do believe that Dell does sell a direct attached disk option for | >>> | the 2950/1950 called the PERC5/e. It's essentially an LSI MPT-SAS | >>> | controller that directly replaces the PERC5/i card that you have now. | >>> | It should be able to control all 6 disk slots, and can do both SAS | >>> | and SATA. | >>> I've been told the PERC5/e and PERC5/i are the same except for PCI | >>> sub-device ID and are both the mfi(4) RAID controllers. They do | >>> have a mpt(4) based card but it only supports 4 bays. I'm not sure | >>> what it's real name is but we have some lying around for random | >>> testing. I don't leave them in machines. | >> | >> We should get a definitive answer on this. | > | > We asked our Dell salesman and he confirmed that there's a non disk | > array card for this machine, | > but it only supports 4 disks, not 6. | | Ok, I thought that the 4 disk option just routed the motherboard SATA | connectors to the backplane, and that there was a 6 disk SAS+SATA option | that put an MPT card into the slot behind the backplane. Oh well. The Dell storage cards are interesting now. The built-in cards are a PCIe card on a horizontal tray the plug in a special PCIe slot by the front. You can take it off the tray, screw on a PC slot bracket then plug it into a PCIe slot. So the same cards can be used for either in the special slot in the PE2950 or in the other Dell machines via a generic PCIe slot. The mpt(4) card only has on SAS connector on that can only plug into one of the SAS back-planes connector. So you are limited to 4 SAS bays. The mfi(4) cards have 2 so you can use all drive bays. Dell's current mpt(4) and mfi(4) cards have been layed out so they can be interchanged with their mounting HW. The only this I don't know is their naming since PERC is for "built-in" and CERC is external. Also I'm not sure what they do for the battery if in generic PCIe mode. They could make a battery that bolts on or piggy back the DIMM like LSI does. I don't know all of the specifics since we order random things that I just make work. It's a fairly smart move since they can offer the same RAID/SAS stuff across their product line and only use 2 cards. Since they share the SAS card and some platforms don't have the space for a lot of drives they probably cost reduced it to one connector versus the 2. Note moving cards around like this is probably not supported but I do things like this to test out things. Doug A.
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