kernel recognizing large (> 2.1 TB) block devices ?
Eric Smith
eric at brouhaha.com
Wed Jan 12 03:17:07 UTC 2005
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.
> 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.
Eric
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