From: Martin Knoblauch <knobi@knobisoft.de>
Subject: Strange performance problems between Linux client and
	Sun/Solaris-10 Server with SAM-FS
Date: Mon, 14 May 2007 04:14:10 -0700 (PDT)
Message-ID: <758936.68723.qm@web32601.mail.mud.yahoo.com>
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Hi,

 we are fighting with a strange performance problem when accessing a
Sun/Solaris-10 server from a Linux NFS client (HP DL380G4, x86_64,
RHEL4U3 user-space, various kernels from  2.6.9-34.ELsmp up to
2.9.21.1).

 The underlying FS on the Sun is SAM-FS (4.5.33) which provides HSM
capabilities. The basic layout is that the "online cache" is relatively
small on "high-speed" FC disks, while the offline data are stored on
cheapish SATA disks and high-speed tapes.

 The problem arises when accessing (reading) a file that is offline on
the Sun. In this case the so-called "stager" brings it back to the
online-cache first, while the client waits for the data to be
available.

 This works fine (staging speed up-to or larger  50 MB/sec) on:

- administrative "stage" request
- accessing the offline file on the Sun-Server itself
- accessing the offline file from a Solaris-10 NFS client

 When doing the same from the Linux Client performance drops below 10
MB/sec. Network performance itself looks good when accessing the file
"online".

 One thing that looks different when doing tcpdump/snoop traces between
the systems is that in the Linux/Solaris case the client seems to send
more READ3 requests (factor > 3) that the Server acknowledges (both in
the online and offline case). In the Solaris/Solaris case the number of
requests and acknowledgements is about the same.

 The remote filesystem is mounted NFS3/TCP with the following
parameters:

xxxx:/net/xxxx/fs03 on /net/xxxx/fs03 type nfs
(rw,hard,intr,bg,nfsvers=3,proto=tcp,timeo=600,rsize=32768,wsize=32768,addr=yy.yy.yy.yy)

 We are already talking to the Sun people, but they cannot reproduce.
So I put my hope for some insight on this list.

Cheers
Martin
PS: Please CC me on replies, as I am only getting the digest


------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www:   http://www.knobisoft.de

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