What are the potential causes of a system _partially_ hanging for 1
minute or more -- other than a SCSI adapter/driver/disk problem?
Several people have said that the problem must be with the
adapter/driver/disk, but I'm having my doubts.
I've now found that during these 'hangs' some simple commands work: ls,
cat, file (this would indicate to me that it is reading the disk). But I
can't do "ls -l" and just about anything else (the Apache web server
just says 'internal configuration error' whenever someone tries to
access a page). This behaviour is consistent.
Also, the problem is identical when trying to access files on my IDE
drive as it is on the SCSI drives. I had thought it might have something
to do with running RAID-1, but it hangs the same when the system is in
degraded mode with only one SCSI disk operational.
After a month and a half of fighting this problem, I'll take _any_
suggestions on what to try next. So far, in attempting to fix this I've
tried, without success:
* replacing the original SCSI cable with a custom, 3' teflon LVD
cable with an active negation terminator (CS Electronics,$125).
* upgrading the AIC7xxx driver from 5.1.21 to 5.1.29;
* adding a hard disk fan for extra cooling;
* setting up remote logging to catch any error message (none logged);
* adding aix7xxx verbose debugging (nothing);
* removing the IDE drives and kernel support for IDE;
* lowering the front bus speed from 100.3Mhz to 88.3 (underclocking
CPU), based on another hunch;
* checking IRQs for conflicts;
* compiling the kernel with and without tagged command queuing,
with more and fewer max commands;
* switching kernels from 2.1.10 to 2.1.14 with appropriate RAID
patches;
* reducing SCSI controller speed (as previously mentioned) on Seagate
drives to 40MB from 80MB (appears to reduce but not eliminate
problem);
* repeatedly searching the archives of mailing lists for aic7xxx,
linux-scsi, Adaptec, and ASUS -- no luck.
Current Configuration:
----------------------
2.2.14 kernel with raid-2.2.14-B1 patch
Adaptec 2940U2W (2.20.0 bios)
2xSeagateST39103LW (U2W drives)
Single PII 400Mhz
ASUS P3B-F motherboard (Intel 440BX AGPset)
CPU Bus/PCI Freq - 100.3/33.43
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