[Info-vax] Sudden problems with slow sftp transfers and slow disk accesses

[gwilliams at cfa.harvard.edu]

Cluster of 8 Alpha boxes running V8.3 + patches, recently moved
from one building to another.  Since the move, we've been experiencing
odd behaviors: very slow network access (via sftp) and slow disk IO.

Disk storage is mostly on three eternal disk boxes (five three-member
shadow sets).  No errors are reported via SHOW DEV DSA.

Network cards on all machines are set to 100 MB, full duplex,
non-autonegotiate, connected via an 8-port GB switch.

An sftp from one of our machine to a local Linux system transferred 288 KB
of a ~ 6MB file in the first second, the current rate is now down to 5KB/s.
MONITOR PROCESS/TOPCPU doesn't show the process getting even 1% of the
CPU and there is nothing else running on the system.  Another attempt on
the same file transferred 1.5 MB in the first second, then dropped to
< 50 KB/s.

SHOW MEMORY doesn't show any problems.

A filing operation merging two large files took a matter of seconds
when both files were on a locally-attached disk.  When both files were
on a shadow set, the merge took 6+ minutes.  MONITOR LOCK while
running the latter test showed ENQ/DEQ rates < 1.

Image activation is slow.  It can take several seconds to begin
running an .exe stored on the shadow set.  

MCR SCACP SHOW LAN_DEV/ALL showed numerous errors occurring over the
past 24 hours, so this evening we replaced the switch connecting these
8 machines.  Errors are continuing to appear.

What am I missing?

Gareth