File Services
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Titan SiliconServer
After a Logical Unit has been created and the iSCSI domain name has been set, an iSCSI Target
must be created to allow access to the Logical Unit. A maximum of 32 Logical Units can be
configured for each iSCSI Target.
Logical Unit Management
An iSCSI Logical Unit is a file within one of Titan’s File Systems. Such a file must have a
.iscsi
extension to identify it as an iSCSI Logical Unit. However, apart from this extension there is no
other way to determine that a file does indeed represent a Logical Unit.
Note:
BlueArc recommends that all iSCSI Logical Units are placed within a
well-known directory, for example
/.iscsi/
. This provides a single repository
for the Logical Units in a known location.
Logical Unit Security
As Logical Units are files, they can be accessed over other protocols, such as CIFS and NFS.
This renders the Logical Units vulnerable to malicious users who can modify, rename, delete or
otherwise affect them.
Note:
BlueArc recommends that sufficient security is set on either the
Logical Units' files, the directory in which they reside, or both, to prevent
unwanted accesses. If possible, Logical Units should be placed in a directory
that isn't accessible via users' CIFS shares or NFS exports.
Concurrent Access to Logical Units
The Titan SiliconServer's iSCSI implementation allows multiple initiators to connect to a single
Logical Unit. This is necessary for applications and operating systems that support, or rely
upon, concurrent file system access. However, concurrent access can be detrimental to a client
machine when the client is oblivious to others accessing the file system.
For example, imagine two independent Microsoft Windows clients who both connect to the same
Logical Unit, containing an NTFS file system. If each client modifies data, metadata, and system
files without any knowledge of the other, these conflicting disk updates will quickly corrupt the
file system. Such a scenario should be strictly avoided.
As another example, imagine a Logical Unit that contains two distinct NTFS partitions. Suppose
that one Microsoft Windows client connects to the Logical Unit and accesses only the first
partition. Then, a second, independent Microsoft Windows client connects to the Logical Unit
and accesses only the second partition. Even though the two clients are accessing separate
partitions within the Logical Unit, this scenario should be avoided because a Microsoft iSCSI
client will attempt to mount each partition it encounters on the Logical Unit. When a Microsoft
Windows client mounts an NTFS partition, it updates system files. Therefore, mounting an
NTFS partition concurrently from separate Microsoft Windows clients will cause conflicting
system file updates and will cause one or both of the clients to fail.
