May 2014

==== Background ====

During high activity, the linux kernel seems to give priority to the
CPU and IO processes vs the network, while freebsd seems to be the
other way around.  As a result, the linux slaves require a higher
read timeout compared to freebsd, so I have raised the default
value of the master->slave write timeout in Nbsp so that linux slaves
do not need manual configuration.

During high activity, Linux works out the queues better, at the
expense of poorer network response. FreeBSD is the other way around;
so the queues accumulate somewhat more, but eventually they are worked out
as well. It just takes longer to work the backlog, but it responds better.

So, performance-wise I cannot prefer one over the other. I prefer
FreeBSD, but because I am a freebsd die hard fan.

I summary, I am using FreeBSD in the ingest machine(s),
but in the slaves I am using Linux (Debian) because the current version of
Gempak does not compile in FreeBSD-10.

== Linux (Debian) ==

In Linux the best setup is to use several disks with lvm for
/var/noaaport/data, and a //tmpfs// for /var/noaaport/nbsp/spool. In fstab

<code>
  tmpfs /var/noaaport/nbsp/spool tmpfs  size=6G   0     0
</code>

This setup has been working perfectly.

== FreeBSD ==

In FreeBSD, I also tried a tmpfs for the spool, by setiing in fstab,

<code>
  tmpfs   /var/noaaport/nbsp/spool tmpfs  rw      0       0
</code>

but it dod not work well. After 1-2 days the kernel panics, and it happened
in different machines with very different hardware. It seems
that tmpfs in FreeBSD is not robust enough for this application.

Therefore in FreeBSD I use several disks with zfs, which is
what I have been using since zfs was introduced.

==== Examples ====

== Linux ==

<code>
  # pvcreate /dev/sdb /dev/sdc /dev/sdd
  # vgcreate lvm0 /dev/sdb /dev/sdc /dev/sdd
  # lvcreate -n noaaport -l 100%FREE lvm0
  # mkfs -t ext4 /dev/lvm0/noaaport
</code>

In /etc/fstab

<code>
  /dev/lvm0/noaaport     /var/noaaport     ext4       defaults    0 2
  tmpfs /var/noaaport/nbsp/spool	    tmpfs      size=6G	   0 0
</code>

Another option, similat to the FreeBSD setup below, is

<code>
  # lvcreate -n noaaport-nbsp-spool -L 6G lvm0
  # lvcreate -n noaaport-data -l 100%FREE lvm0
  # mkfs -t ext4 /dev/lvm0/noaaport-nbsp-spool
  # mkfs -t ext4 /dev/lvm0/noaaport-data
</code>

and then in /etc/fstab

<code>
  /dev/lvm0/noaaport-data /var/noaaport/data ext4 defaults    0 2
  /dev/lvm0/noaaport-nbsp-spool /var/noaaport/nbsp/spool ext4 defaults,noatime 0 2
</code>

== FreeBSD ==

<code>
  # zpool create zpool0 da1 da2 da3
  # zfs create -o mountpoint=/var/noaaport/nbsp/spool -o atime=off zpool0/noaaport-nbsp-spool
  # zfs create -o mountpoint=/var/noaaport/data -o atime=off zpool0/noaaport-data
</code>