Extending your zfs pool with multiple devices

Zaphod Beeblebrox zbeeble at gmail.com
Thu Sep 2 21:26:36 UTC 2010

[regarding getting more disks in a machine]

On Thu, Sep 2, 2010 at 12:47 PM, Joshua Boyd <boydjd at jbip.net> wrote:
> You need an HP SAS expander card in the new box, and an HBA in your primary
> box with external ports to hook it into.
> Then the drives in the other box will show up as local drives on your
> primary box.
> You don't even need an operating system on the second box, it just needs
> enough hardware in it to supply power to the SAS expander.

An inexpensive option are SATA port replicators.  Think SATA switch or
hub.  1:4 is common and cheap.

I have a motherboard with intel ICH10 chipset.  It commonly provides 6
ports.  This chipset is happy to configure port replicators.  Meaning
you can put 24 drives on this motherboard.

Be warned that many SATA chipsets (even plugin cards) will not work
with port replicators...

But the ICH10 does and it makes a wonderfully cheap ZFS server.

With 1.5T disks, I find that the 4 to 1 multipliers have a small
effect on speed.  The 4 drives I have on the multipler are saturated
at 100% a little bit more than the drives directly connected.
Essentially you have 3 gigabit for 4 drives instead of 3 gigabit for 1

The ICH10 motherboard ports can be connected to the back of your
system by cables and faceplaces that deliver eSATA connectors.  I have
my drives in a case that delivers eSATA (or USB).  One USB for 4
drives was a dog, but the eSATA conneciton works well.

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