by April 3, 2007 0 comments

Sanjay Majumder with help from Swapnil Arora and Vijay Chauhan

In our last issue we discussed how to setup an iSCSI based storage using
ordinary Windows and Linux based machines. This time, we’ll go further and build
a similar cluster, but using a different software called Openfiler. It’s a very
powerful storage software that can be used for building both a NAS or a SAN. Not
only that, but we also ran our standard set of tests on it to see how well it
performs. The results were astonishing as you’ll soon find out. Before we get
into the setup, let’s take a quick recap of what all you need to setup this
storage cluster.

The setup required for building the cluster remains more or less the same as
last time. You’ll need ordinary machines with some storage space. We used 10 P4
machines with 256 MB RAM, 40 GB HDD, and 1 Gbps network card. They all need to
be hooked to a Gibabit Ethernet Switch. Plus you will need an eleventh machine
running Windows 2003 Server.

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Primary Link:

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On CD:PCQXtreme System/labs/iscsitarget-0.4.14.tar.gz

This will act as the controller for aggregating the storage from the
remaining ten machines. We have given ISO images of Openfiler on this month’s
DVD. These are for both 32 and 64 bit machines. We used the 32-bit version. Just
be sure that when you burn the ISO on a CD, then keep the writing speed at 4x.
What you’ll get will be a bootable CD.

Prepare storage targets
After creating the CD, boot one of the cluster machines from it. The bootup will
show a wizard driven installation screen. Just click next to start off, and on
the next screen select the language to “English” and move to keyboard selection.
Here select “U.S English” and on the subsequent screen you will be asked to do
disk partitioning using Disk Druid. By default openfiler takes up the first 6- 8
GB on the first disk it finds on the system. But we suggest you choose the
manual partitioning option and set boot to 100 MB, root (/) to one GB and swap
partition to 500 MB if you are using 256 MB RAM on the machine (which we were).

Once you are done, click on Ok and move on. Keep the grub configuration as
default, and you’ll be then taken to the network configuration screen. If you
are using a DHCP server on this isolated network, then tick the DHCP option.
Otherwise give a manual IP and click next. Now you will be asked to set the
time. Finally, the installer will ask you to set the root password. Once you are
through with the installation, reboot the machine. After booting, you will see
the URL on its console, from where you can configure the entire box as an iSCSI
target storage. Run this installation on all the machines in your storage

You have to manually
create the partitions on each node of your storage cluster. Choose Partition
Type as “Physical Volume”.

Once you’ve created the
physical partitions, you need to create a volume group from it. This comes
in handy if you have multiple hard drives on a machine.

Once you’ve created a
volume group, you need to convert it into an iSCI file system and define how
much of the partition space will be allocated to it.

Configuring the cluster
Before configuring the openfiler based cluster boxes, hook up the controller
machine to the same network subnet as these boxes. You will then be able to
access the openfiler administration web interface of each machine from the
controller itself. Fire up a web browser on the controller machine and open the
interface of any of the cluster boxes by entering the URL https://<IP_address_of_openfilebox>:
446. Note that it’s an https connection (secure http) and not an ordinary http
connection. You’ll get a login screen. Give usrename as “openfiler” and password
as “password”. Once logged in, you’ll see all the administrative options like
Accounts, Volumes, Quota, shares, Services and General. First go to the General
option and you will get “Local network Connection” screen. Give any name to the
network, let’s say “local”. Then give the IP subnet, where the machines are
hosted, for example we have used “” and finally give the subnet mask
of the subnet as “”. Once done, click on the update button.

By default, the iSCSI
target service is disabled. In order for the storage cluster to

Create iSCSI volumes
From the same interface select the “Volumes” option and then from its submenu
select “Physical Storage Mgmt”. It will show you a list of physical hard disks
on the box and their partitions. On the same screen you will find “Edit Disk”
header, through which you can edit the physical disk parameters (denoted as
/dev/had). Click on parameter and scroll down to the bottom of the web page.
Here you will see the remaining unallocated disk partition. By default
partitions are set for extended partition, change settings to “Physical Volumes”
and click on “Create” button. Even though it will show that partition is created
instantly, wait for a few minutes because creation of partition is still going
on in the background. Our advice is to wait for at least 15 to 20 minutes after
executing this process. Then come to “Volume Group Mgmt” and scroll-down the
page. Here you will be asked to create the volume group of the partitions.

Give any name to the volume group. For example, we called it “vol_iscsi1”.
Then tick on the physical volume partition that you have created above. From the
given list, click the “update” button. Now come to the “Create New Volume”
option and click on that. You will be asked to fill the volume name and
description of the volume that you want to create. Give any name that suits you
and then on the same web page you have to define the volume size. A slider is
given to adjust the volume size, slide the slider towards the end and maximize
size. Then you have to select the file system type for the volume. By default it
is set to ext3 but you have to select “iSCSI” from the drop down menu and click
on create button. Once the volume is created, it will show the health of the
volume as a pie chart.

Enable iSCSI services
Now you have to enable access to this volume for controller. For this on the
same page, where it’s showing the health of the just-created volume, you will
see a “Properties” parameter and under that you will find “Edit” hyperlink.
Click on that and it will bring edit volume- properties page.

Scroll down the page to bottom and you will find “Volume Host Access”
property, which is by default set to “Deny”. Set this to “Allow” and click
“Update” button to save the settings. Finally you have to start the iSCSI target
services on the controller box, so that the volume that you created above can be
exposed to the outside world as a block device. For this, select “Service”
option given on top of the administrative web page. It will list the name of the
services with enable/disable options that openfiler is offering currently.

Identify iSCSI service from the list and enable the service. With this one of
your openfiler boxes is ready and acting as ISCSI target.

You have to follow the same process for all openfiler boxes you will be using
for your storage farm.

All iSCSI target disks can
be viewed together from the Windows based controller

Configuring controller
We have to accumulate and aggregate all storage hosted on different openfiler
boxes into a single storage. For this we have used a controller machine running
windows, where all the storage from openfiler boxes will be aggregated as a
single huge windows volume and in future can be shared by users on the network.

 To access all openfiler boxes, which are being exposed on the IP
network, you need a software called iSCSI initiator on the controller machine.
Initiator is available for both Windows and Linux. Here we have used Microsoft
iSCSI initiator, which is available free for download at

Install this software on the controller and you will get Microsoft Initiator
icon on your desktop. Double-click on this and you will get its interface with
four tabs (General, Discovery, Targets, Persistent target and Bound volumes/
devices). Select the discovery tab and add all the IP addresses of different
openfiller boxes that you are using in your cluster. Then select “Targets” tab
and you will find the names of all the targets with their status.

On the same screen come down and select the “Logon” button, you will get a
popup screen with logon to target options. Here enable both options
“Automatically restore this computer when the system boots” and “Enable
multipath” and then click ok to apply the settings. After this come to “Bind
Volumes/Devices” tab and then click “Bind All” button.

Now go to your Management Console and open Disk Management. If you’ve setup
the target machines in the initiator correctly, you will see a disconnected new
drive in your Disk Management console. Right click on the disconnected drive and
select “Initiate” option from its context menu. This will run a wizard to
initiate and convert the drives into a dynamic disk. Select all the disks except
disk0, which is Windows physical C: drive. Now on the wizard press next and then
finish button to convert disk to dynamic volume. Till now all the disks will be
shown as an unallocated storage. Now again select the disk1 and right-click on
it, from the context menu select “New Volume”, which will open another wizard
for creating fresh volume. Click next, on this screen you would be asked to
select the type of volume you want to create. Select “Spanned” and click next.
Add all the disks to the spanned volume and click next. Now on next screen give
the volume name and drive letter and don’t select quick format. Then click
finish button to close the wizard. This process may take a few minutes, because
it’s formatting this aggregated huge volume to NTFS file system. Once the
process is completed you will see a huge single volume in terabytes as a Windows
physical disk. This drive is treated just like a local hardware drive, but it is
all done over the network. You can further share this volume to the network

How it performs
We also measured the performance of this storage cluster using Iometer. To test
this we connected two Win XP P4 machines running IOMeter to the same gigabit
switch as the storage cluster. We created a share on the spanned volume of the
storage cluster and mapped it as a local drive on the initiator. In Iometer we
created four workers on each machine and targeted each with the mapped drive. To
stress the storage cluster we used 64 K and 128 K transfer request sizes (the
number of bytes read or written in each I/O request) and did 100% random and
sequential read and write of data. We ran these tests three times, for 2, 5 and
10 minutes. The tests basically measured two performance parameters, namely
total input/output operations per second (IOPS) and MB/sec throughput. Just to
see where it stands, we compared the results of this cluster against those
obtained in our NAS shootout done earlier this year (PCQuest, Feb 2007 issue).
Our cluster gave the best results in 100% random reads, which is understandable
since the storage is actually split across multiple machines. On the other hand,
it gave the lowest performance in the sequential read test. This basically
reflects the performance of each individual drive on each machine of the
cluster, since the writing is happening sequentially. The results were average
in the remaining two tests. This kind of a cluster is good for applications
requiring heavy simultaneous read operations.

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