[8326] in linux-scsi channel archive
Re: Problem
daemon@ATHENA.MIT.EDU (Mark Veteikis)
Wed Mar 8 19:39:45 2000
From: Mark Veteikis <mark@iphase.com>
Message-Id: <200003082255.QAA28167@hera.Iphase.COM>
To: sjbuller@us.ibm.com
Date: Wed, 8 Mar 2000 16:55:05 -0600 (CST)
Cc: eric@estinc.com (Eric Lee Green), linux-scsi@vger.rutgers.edu
In-Reply-To: <8725689C.007BD4E8.00@d53mta02h.boulder.ibm.com> from "sjbuller@us.ibm.com" at Mar 08, 2000 03:32:32 PM
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>
>
> >There *IS* one limitation in the Linux SCSI subsystem that may be biting
> >you -- it only addresses up to 16 devices. That's all, folks! Obviously
> >this is something that has to be changed before Linux can be taken
> >seriously in the high-end storage department.
See earlier post on setting "max_id" in host structure.
An alternate methodology is to set max_channels up to be "virtual"
scsi busses and use 16 per virtual channel.
> There are lots of caveats to the above mentioned 16 device limit. RH6.1
> (kernel 2.2.12-20) will do more than 16 devices/LUNs IF you run the
> /dev/MAKEDEV script to create more devices ("out of box" stops at
> /dev/sdpX).
>
> The real killer is the limit of 4 devices on a secondary SCSI bus due to
> SD_EXTRA_DEVS. I'm testing a 11.2TB subsystem for Linux compatibility.
> You ever tried to hide 11.2TB behind a grand total of FOUR LUNS?!? ;)
> I've heard future releases will take this to 40, but you can fit
> 127 devices on a FC-AL. sigh.
I have seen no problems tuning SD_EXTRA_DEVS up to 40 and beyond.
If necessary I'll test with 80+ drives to verify.
--
Mark Veteikis mark@iphase.com 1-214-654-5257
Interphase Corp. 13800 Senlac Dallas Tx. 75234
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