On Tuesday 11 January 2005 22:17, Eric Smith wrote: > Randall A. Jones wrote: > > I have a 4.8TB RAID device attached to a FC3 system via SCSI. > > The system recognizes a RAID LUN volume of 2.1TB or less without any > > problem. When I configure the RAID as a full 4.8TB LUN, the kernel > > fails to recognize its actual size > > Peter Arremann wrote: > > standard scsi in itsself has a limit of 2TB (32bit block adressing with > > 512 byte blocks). LSI (others have followed since) has new enhancements > > (http://www.infortrend.com/%5CNews%5C20041006%5Cf_64Bit_LBA.htm) but I > > know of no storage devices that currently implement that since it is not > > an official standard and seems to have some other problems.... > > It most certainly is an official standard. It's the READ(16) and WRITE(16) > commands in SCSI-3, and Google turns up evidence that Linux 2.5.x added > support for them in December 2002. Perhaps that support hasn't been > retrofitted to all drivers, or perhaps Randall is encountering a limit > somewhere else in the kernel. go to T10.org - the guys that write the scsi standards documents - go to scsi-3 standards documents and then follow the link to any of the scsi-3 docs like sbc... then read the first line and look where the URL takes you - it says DRAFTS... and as such its not an official standard and anyone who has been around long enough will tell you how wonderfully compatible the implemenations of scsi-2 under the first few draft revisions... > > Your RAID should not allow you that or at least warn you if it supports > > the extension (what model is it?) but I know for sure that the adaptec > > 7xxx chips don't. > > AIC7xxx chips don't care what the length of the command is. It's up to > the driver. I have no idea whether the Linux aic7xxx driver supports > them. The chip cares - it is the one to emit the command on the scsi bus. If it has no knowledge of that command, then how will it to that? There are several pieces that need to work together - the linux driver needs to understand 16 byte commands, the firmware on your controller needs to support it and then finally the chip on the controller needs to be able to do it. I had a few discussions with two techs from adaptec that both agreed that up to U2 (29160 and newer) the aic7xxx is not able to do this. Newer models can with firmware and driver updates but Adaptec has not (and more than likely will not in the near term or ever) release firmware updates. The drivers are of course no real issue since linux doesn't use the official adaptec driver set... I would love for you to prove me wrong since I have tons of (old and new) adaptec hardware that I would like to use with large arrays but with the answers I got I don't think its going to happen... Peter.
