Duncansapien’s Techblog

Overview

The requirement is to connect an EMC Celerra NAS device, via iSCSI, to a Fedora 8 (and later, perhaps, 9) Linux system.

Relevant Information

Most information is still in paper form.

iSCSI-initiator-utils is the name of the software package used here, version 6.2.0.865, and the online repository for this package is http://fr.rpmfind.net/linux/rpm2html/search.php?query=iscsi-initiator-utils .

Routing with Multiple NICS - in test environment, one NIC uses 80 (public) subnet and the other a private subnet, no problem. In the live environment, may want two NICS, but one dedicated for iSCSI usage. How to ensure each NIC doesn’t forward/route to the other NIC? Answer. Background on the commands used in the answer - "Guide to IP Layer Network Administration with Linux".

Best Site

This site - RedHat Tips and Tricks - provides the best overview of iSCSI on Fedora systems (actually RedHat but it matches closely with my own Fedora 8 experience).

Also this information (source) is worth knowing!

# install the iscsi utils

yum -y install iscsi-initiator-utils

# change initiator name for new install of iscsi package

/etc/iscsi/initiator.name - InitiatorName=iqn.1991-05.com.microsoft:

# find targets available to the machine

/sbin/iscsiadm -m discovery -t sendtargets -p

# connect and login to target

/sbin/iscsiadm -m node -T :-1 -p -l

# persist the connection for startup

/sbin/iscsiadm -m node -T :-1 -p –op update -n node.conn[0].startup -v automatic

#MOST IMPORTANTLY

vi /etc/fstab

device mount point FS Options Backup fsck

/dev/sda /data2 ext3 _netdev,noatime 0 0

# logout of connection

/sbin/iscsiadm -m node -T :-1 -p -u

Dedicated NICS for iSCSI

Best practice - use a dedicated NIC for iSCSI on a private LAN. But in the current case, the SAN device resides on a public network within the University. Still wishing to use a dedicated NIC for iSCSI traffic, how do we go about it?

After looking at all sort of routing issues, one site suggests simply using iptables to disable port 3260 - which handles iSCSI traffic - on the NIC which you don’t want such traffic one.

Overview

VMware works best with SAN-based storage and SANS may be connected to a VMware GSX server via fibre-channel, iSCSI or NFS. This means that the VMFS (VMware File System) on which VMs are created may be housed on a SAN, and connection to that SAN is via fibre/iSCSI or NFS.

Indeed, any individual VM may be configured to use iSCSI storage by itself e.g. a Windows Server 2003 VM may be configured to use iSCSI storage directly. So there is flexibility in how an iSCSI SAN is used by VMware hosts. For simplicity, configuring an iSCSI SAN to offer a chunk of space to the VMware GSX server on which to create all the VMs seems a good choice, but I’m sure there’s room for discussion on this.

Some systems don’t run VMware (yet :o) but nonetheless wish iSCSI connectivity, since it comes close to Fibre Channel speeds at significantly lower cost - assuming one has fast, reliable switches!

A variety of iSCSI target software is available.

OpenFiler

OpenFiler - an open-source, linux-based solution here running in a pre-configured Virtual Machine. Has a huge number of options (NAS, iSCSI).

Open-e

Open-e - software that boots from a USB device, turning all storage on the attached host into iSCSI target storage. There are three product lines compared here (you’ll need to do the comparison yourself :o)

1. Open-e DSS - "Data Storage Server" (NAS and iSCSI), including DSS Lite (1Tb limit)
2. Open-e NAS R3 - "Network Attached Storage R3"
3. Open-e iSCSI R3

The DSS-Lite product - free and limited to 1Tb storage - was downloaded in SML to N:admininstallVMWareDSS_Lite where N: maps to Novell server \somfs2. Thanks to Andrew Aitken in HWU for alerting me to this software.

But how reliable is this software? Well, here’s a company selling a 24Tb iSCSI SAN using Open-e Enterprise, so they clearly think it’s robust.

SanMelody

Sanmelody - iSCSI software which turns a Windows host into an iSCSI target. They also have a low-cost ‘Lite’ version but SML staff had difficulty downloading this and making payment, as it seems tied to US customers only. Their loss!

Overview

The most flexible arrangement for connection of Vmware hosts to their data store is via either a Fibre Switch (expensive) or ethernet using iSCSI and gigabit network connections.

Testing iSCSI

Using iSCSI means that VMware servers could be in separate buildings, one acting primarily as a fallback to the other. Data could be stored on a device with iSCSI target software (such as Windows Storage Server 2003). Connection from host-to-data could use MPIO (multi-path input output) - slightly beyond the scope of this entry.

To test iSCSI one needs

• a low-cost gigabit switch
• a low-cost gigabit PCI ethernet adapter (for the storage device)
• low-cost iSCSI Target (such as San Melody Lite)
• Cat 6 ethernet cables

A suitable switch is the Netgear ProSafe™ 5 Port Gigabit (10/100/1000) Ethernet Desktop Switch, at just under £40.00 inc VAT. Also a low-cost Gigabit ethernet adapter is the NetGear Ga311.

Update Jan 18th 2008: The above switch and several Cat6 (gigabit) cables have arrived.