Thanks for the information. I have some questions.
 You said "zfs uses large amounts of memory for its cache". If I
understand correctly, it is not that it uses large amounts, it is that it uses
all memory available. If this is an accurate picture, then it should be just
as happy with 128MB as it is with 4GB. The result would simply be less of a
cache/buffer between clients and the physical disk. It also seems like any
congestion should show up fairly soon, not gradually over 12 hours! Certainly
limiting the ARC cache is something I will try, but it does not make sense to
me. Can you help me along?
 Regarding zfs vs. nfs, the reference talks about unneeded cache flushes
dragging down throughput to NVRAM buffered disks. The flushes were designed
for physical rotating disks. I am using physical, rotating disks, so it seems
like the changes that they suggest for NVRAM buffered disks would not be
appropriate for me, and that the default behavior designed for physical
rotating disks would be what I want. What am I missing?
 I also get ~4MB/second throughput NFS to disk with compression disabled,
and 3MB/sec with gzip-9 for the first hour or two. This is nothing to brag
about and I had planned eventually to look into making it faster, but this
pales compared to the 100KB/second it has degraded to over 12 hours. Were your
comments aimed at helping me get faster NFS throughput, or at addressing the
immediate gross problem?
Thanks again for taking the time to help.
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