Mailing-List: contact derby-user-help@db.apache.org; run by ezmlm
Precedence: bulk
Reply-To: "Derby Discussion" <derby-user@db.apache.org>
Received-SPF: pass (athena.apache.org: domain of brett.wooldridge@gmail.com
 designates 209.85.214.44 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:date:message-id:subject:from:to:content-type
         :content-transfer-encoding;
        b=BKlq3AgGzu4Xw2vbbULihw3FMzudFm8Sh0w0ElATfEUn/0BaJti32xqSUdi9zBV22l
         uWPQeAVkOsymOct3xVkVn8kzSFMM2LB/MZuLkYzsFCosvwZqnHX1rgbWbJK3hi22TIqD
         IWT1x0r7N7ebHZfXrAqZI8mqqi+o06QqdK/s8=
MIME-Version: 1.0
Date: Wed, 8 Jun 2011 22:09:33 +0900
Message-ID: <BANLkTiktXYvLz2o_ndaWsutLVPwtTN0OnA@mail.gmail.com>
Subject: LOBs/Replication
From: Brett Wooldridge <brett.wooldridge@gmail.com>
To: Derby Discussion <derby-user@db.apache.org>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

I have a question about replication as it pertains to LOBs (BLOBs and CLOBs=
).
According to the documentation...

If the master looses connection with the slave, "transactions are
allowed to continue
processing while the master tries to reconnect with the slave. Log
records generated
while the connection is down are buffered in main memory. If the log
buffer reaches
its size limit before the connection can be reestablished, the master
replication
functionality is stopped."

And the documentation for=A0derby.replication.logBufferSize says the
maximum size of
the buffer is=A01048576 (1MB).

This seems to imply that if I have a database in which I store LOBs
which are, for
example, 256K in size, and the connection between master and slave is sever=
ed,
I can perform 4 inserts or less before the master gives up. =A0Is this
so? =A0If this is in fact
the case, I would like to file a request that this limit be=A0raised
considerably or eliminated
altogether.

I have two servers (master and slave)=A0running 64-bit JVMs, 64GB of memory=
 each,
SSD drives, connected by 10GbE=A0fiber. =A0I would like to dedicate=A0as
much memory as I
want to deal with a disconnect/resume scenario (to avoid the onerous
failover). =A0At an
insertion rate of 16 rows per=A0second (~4MB), currently the setup would
tolerate a
connection interruption of a fraction=A0of a second. =A0A 1GB buffer would
afford a connection
interruption of ~250 seconds (for=A0example, rebooting the fiber switch).

Last question, aimed at devs, why does Derby even bother to buffer
logs in memory?
Can't it just keep an offset/marker into the transaction log files,
and replay transactions
from there, rather than buffering them in memory?

Regards,
Brett