Thanks to all who responded.
The consensus is that symbolic links are slower when opening a file,
and they do create an additional resource-management issue to be tracked,
but the impact depends on the application.
My application opens approx. 256 files at startup, and
128 are closed, renamed, and reopened at midnite.
The very large number of I/O's on the open files should be
unaffected. My task, now, is to test, test, test....
Seth
Thanks to:
Two list members suggested lofs, loopback file system,
which is effectively a mount point off another mounted partition:
Viet_Q_Hoang <vhoang@lucent.com>
Birger Wathne <Birger.Wathne@getronics.no>
Thanks to others who shared their experience:
Brett Lymn <blymn@baea.com.au>
"Brion Leary" <brion@dia.state.ma.us>
Kevin Sheehan {Consulting Poster Child} <kevin@joltin.com>
Edwards Philip M Ctr AFRL/SNRR <Philip.Edwards@wpafb.af.mil>
Glenn Stafford <glenns@trdlnk.com>
Michael Hocke <mhocke@globix.net>
"Vince Merrell" <blipvert@blipvert.screaming.net>
>>> "Seth Rothenberg" <SROTHENB@montefiore.org> 12/02/99 12:05PM >>>
Sun Managers,
We recently changed our file systems to move our
application from a single filesystem striped across 8 disks,
to 3 file systems striped across 10 disks, i.e.,
from /dg (8 disks) to
/dg (2), /dg/dghome/log (3), and /dg/dghome/queue (5).
(and all of them are mirrored).
(See below for a URL)
This change yielded some improvement in throughput.
Now, we want to split this into two application trees,
i.e., /dg, /dg/dghome1/log, /dg/dghome1/queue
and /dg, /dg/dghome2/log, /dg/dghome2/queue
(No additional volume, just divided in half).
I don't have enough disks to make six file systems
on separate disks, and I want to stay with using only
slice 0, which is fastest.
I thought of using symbolic links, eg,
/dg/dghome1/log -> /dg/dghome/log/1/ and
/dg/dghome2/log -> /dg/dghome/log/2/ and
/dg/dghome1/queue -> /dg/dghome/queue/1/ and
/dg/dghome2/queue -> /dg/dghome/queue/2/
However, my application vendor warns that
symbolic links are slower than direct mounts.
(That's the reason these file systems are mounted
under the application user's home directory)
I wonder if anyone has experience making this
type of decision?
Thanks
Seth
PS the procedure we followed to move
our application from one SDS file system to
three with minimal downtime is documented.
The archive can be found at
http://www.eng.auburn.edu/pub/mail-lists/ssa-managers.
Follow the hints link.
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