SOLVED! (was: Re: slow performance on MS-Access database)
davecb at canada.sun.com
Wed Jan 12 13:30:36 GMT 2000
Stephan Roeller wrote:
> Problem: access on a MS-Access database file is incredible slow
> (80 Ks/sec) while normal file i/o is between 2 and 4 Megs/sec.
> Files und Access database reside on the same share.
> Disabling SMB read raw requests improves thruput on Access database
> to 600 Ks/sec while decreasing normal file i/o also to 600 Ks/sec
> (even on large files, f.e. sr2bof97.exe <=> 23 Megs).
Mr. Roeller created a virtual server for the database only,
and got the performance increase without affecting
other services. I thought this **might** work, but wasn't
sure. I'm very pleased it did.
The caveats he noted were:
> It's essential to offer domain logons and home directories through
> your 'main' smb.conf, the aliased servers won't do!
A mysterioso for you guys, though:
> thruput accessing the MS-Access database file from server database-1
> improved to 2 Megs/sec!!!
> That's the one funny thing I definitly do not understand ...
> - 'single' server, "read raw = no" => 600 Ks/sec
> - 'multiple' server, "read raw = no" => 2 Megs/sec
> Strange, but I _definetly_ won't complain :-)) Customer either!
> Maybe it's just overhead searching and serving the file from a share
> holding approximatly 35.000 files compared to an extra share just
> holding 10-20 files.
> (Nevertheless: using the database from an extra share just holding
> this one file, using "read raw = yes", still gives you 80 Ks/sec ...)
Can anyone comment on this, and the underlying problem:
read raw vs Access???
My current suspicions:
1) two servers implies two tcp connections, and the two
may be giving better throughput than one
2) read raw is hogging the connection doing large transfers
so that Access is having a hard time getting a
word in edgewise, thus increasing its latency
and therefor decreasing observed speed.
I'll give those about 30% probability (;-))
David Collier-Brown, | Always do right. This will gratify some people
185 Ellerslie Ave., | and astonish the rest. -- Mark Twain
Willowdale, Ontario | //www.oreilly.com/catalog/samba/author.html
Work: (905) 415-2849 Home: (416) 223-8968 Email: davecb at canada.sun.com
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