I only received one response to my query about getting better
performance out of my solid-state disk with advfs.
Alan Rollow replied suggesting that I look at the size of each i/o
request. Advfs tries to consolidate multiple writes or reads in to
a single transaction, which can cut down on the transaction rate and
increase total throughput. In my case I am trying to do a lot of
rather random i/o transactions per second (file creates/deletes),
not what advfs is built for.
I haven't had much luck increasing the responsiveness of this file
system but I did find some useful information.
The metadata log for a file domain can be moved with the 'switchlog'
command. This did help a bit. File extents, but not metadata, can
be moved with the 'migrate' command. I use this to move hot-spot
files when necessary. I did not find any easy way to move a file's
metadata. You can play musical chairs adding and removing volumes,
which end up moving metadata but that clearly isn't very workable.
The i/o tuning that Alan suggested can be done with the 'chvol'
command. Chvol can set the i/o consolidation size for reading or
writing, and can turn consolidation off or on altogether. Chvol can
also set the number of 'dirty' pages that advfs will let accumulate
before writing. In my case I am running with cmode off, to let
small i/o happen at higher rates, and set the 'dirty pages'
threshold very high. I have seen some improvement in performance
but not what I am hoping for.
Thanks to Alan for his suggestion.
-- Jeff Hayward
On Mon, 10 Nov 1997, Jeff Hayward wrote:
I have a 2100a 4/300 system which I use for a mail application. The
queue disk area for this system gets hit very hard. I have a
Quantum SSD available from a previous incarnation of the system
which I would like to use to handle the i/o transaction rate, but
I'm having problems.
The SSD is rated at about 1,000 ops/second by the manufacturer. The
model I have is fast/narrow SCSI connected to a KZPAA, so I don't
expect to hit quite that peak performance. I can't seem to get more
than about 120 ops/sec, about 1.5MB/sec (as reported by "monitor")
from the thing using either UFS or ADVFS under my normal workload.
Any hints or tuning advice for getting more out of the drive would
be appreciated.
Semi-related question: Is there a way to tell ADVFS to move a file
or directory metadata to a specific ADVFS volume? The "migrate"
utility will move file extents, but not metadata. If I'm able to
get more performance out of the SSD I'd like to have it handle all
the metadata and log area for the file domain.
Thanks for your help,
--
Jeff Hayward j.hayward_at_ots.utexas.edu
+1 512 471 2432 (v)
Received on Fri Nov 14 1997 - 01:30:45 NZDT