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Many motherboards nowadays have integrated gigabit ethernet that use the Realtek NIC chipset.

The Realtek r8168B network card does not work out of the box in Redhat/Centos 5.3: instead of loading the r8168 driver, modprobe loads the r8169 driver, which is broken as can be seen with ifconfig which shows large amounts of dropped packets. A solution is to download the r8168 driver from the Realtek website and install it using the following steps:

Check whether the built-in driver, r8169.ko (or r8169.o for kernel 2.4.x), is installed.

# lsmod | grep r8169

If it is installed remove it.

# rmmod r8169

Download the R8168B linux driver from here into /root.

Unpack the tarball :

# cd /root
# tar vjxf r8168-8.012.00.tar.bz2

Change to the directory:

# cd r8168-8.012.00

If you are running the target kernel, then you should be able to do :

# make clean modules   
# make install
# depmod -a
# insmod ./src/r8168.ko (or r8168.o in linux kernel 2.4.x)

make sure modprobe knows not to use r8169, and that depmod doesn’t find the r8169 module.

# echo "blacklist r8169" >> /etc/modprobe.d/blacklist
# mv /lib/modules/`uname -r`/kernel/drivers/net/r8169.ko   \ /lib/modules/`uname -r`/kernel/drivers/net/r8169.ko.bak

You can check whether the driver is loaded by using the following commands.

# lsmod | grep r8168
# ifconfig -a

If there is a device name, ethX, shown on the monitor, the linux driver is loaded. Then, you can use the following command to activate it.

# ifconfig ethX up

After this you should not see any more dropped packets reported.

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In this article Barry Mavin, CEO and Chief Software Architect for Recital debunks the myths and misrepresentations surrounding XBase and explains how Recital, an enterprise-class XBase platform, has overcome all the shortfalls and weaknesses of early XBase implementations.

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TIP
If you are using the Oracle Gateway in Recital, make sure the Oracle environment (ORACLE_HOME, ORACLE_SID etc.) is set up before starting the Recital Server.  If not, you will see the error ORA-01019.  A call to the Oracle environment setup script can be added to the /etc/init.d/recital script if your Recital Server is set to run on startup.
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Recital implements SQL-92 and most of the SQL-99 standard for SQL, but also provides lower level navigational data access for performing high transaction throughput. It is the choice of the application developer whether to use SQL, navigational data access, or a combination of both depending upon the type of application being developed.
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If you want details about how storage devices are performing on Redhat/Centos/Fedora use the vmstat and iostat commands.

After installing Centos 5.3 the iostat command is not available. To install it use yum:

# yum install sysstat
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Each Recital table can have one or more data dictionaries to provide a central repository for constraints and other metadata. 

Here's how to set up field validation based on dynamic values from another table.

Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.
open database southwind
alter table products add constraint;
(categoryid set check rlookup(products.categoryid,categories))
The rlookup() function checks whether an expression exists in the index (master or specified) of the specified table .  An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.

If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.

validation


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It would appear that gigabit LAN is not! In fact it often runs at the same speed as 100Mbps LAN. Let's look at why exactly.

After configuring your network you can use the ifconfig command to see what speeds the LAN is connected. Even though 1000Mbps is reported by the card, the reality is that the overall throughtput may well be ~100Mpbs. You can try copying a large file using scp to demonstrate this.

As it turns out, in order to use a gigabit LAN you need to use CAT6 cables. CAT5 and CAT5E are not good enough. End result, the ethernet cards throttle back the speed to reduce dropped packets and errors.

You can find a good article here titled Squeeze Your Gigabit NIC for Top Performance. After tuning up the TCP parameters i found that it made no dfifference. The principal reasons behind low gigabit ethernet performance can be summed up as follows.

  1. Need to use CAT6 cables
  2. Slow Disk speed
  3. Limitations of the PCI bus which the gigabit ethernet cards use

You can get an idea about the disk speed using the hdparm command:

Display the disk partitions and choose the main linux partition which has the / filesystem.

# fdisk -l


Then get disk cache and disk read statistics:

# hdparm -Tt /dev/sda0


On my desktop system the sata disk perfomance is a limiting factor. These were the results:

/dev/sda1:
Timing cached reads:   9984 MB in  2.00 seconds = 4996.41 MB/sec
Timing buffered disk reads:   84 MB in  3.13 seconds =  58.49 MB/sec

Well, that equates to a raw disk read speed of 58.49 * 8 = 467Mbps which is half the speed of a gigabit LAN.

So.. NAS storage with lots of memory looks to be the way to go... If you use the right cables!


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By default Recital uses PAM to authenticate users.  It is also possible to tell PAM to use Kerberos.  Simply replace the existing entries in the /etc/pam.d/recital file with the ones below:

auth       sufficient   pam_krb5.so try_first_pass
auth       sufficient   pam_unix.so shadow nullok try_first_pass
account    required     pam_unix.so broken_shadow
account    [default=bad success=ok user_unknown=ignore] pam_krb5.so
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I am a fan of the previous incarnation of the PlugComputer so I was excited to see that Marvell have unveiled a new PlugComputer dubbed imaginatively "PlugComputer 3.0."

PlugComputer 3.0 Features:

Smaller sleeker design,
More powerful CPU - 2gz Armanda 300 CPU,
120GB 1.8-inch SATA hard drive,
Wifi,
Bluetooth,
10/100/1000 wired Ethernet,
USB 2.0
.
512MB of RAM
512MB of Flash memory


I for one would like to see an additional Ethernet port added to increase application flexibility, for some applications where you are using clustered plugs or even for routing, having multiple Ethernet ports is a must.

Even without multiple ethernet ports, these low power consumption devices really could have a place in SME environments, replacing large cumbersome legacy hardware with compact Linux plug servers.

More information about the PlugComputer can be found here
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And apparently IE9 will support rounded corners.
http://kbala.com/ie-9-supports-corner-radius/
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