The NovaNET Advantage
NovaNET Alliance is unique in the industry as it is the only product that was
designed to handle client-attached devices from the start. This has meant
that the transition to SAN was a natural progression; the designed-in
integration means that NovaNET SAN support is seamless and hence is easy to
setup and use. The standard NovaNET Alliance installation can support SANs
without any further software installs.
Users' biggest fear with SAN solutions is the setup process; NovaNET
addresses device setup in an automated fashion. Using NovaNET 's
plug'n'play style device configuration, a device is initially configured to
NovaNET but to only one system. NovaNET then has the ability to auto-configure
the same device to other systems on the SAN. This functionality is crucial
on SANs where a library with several drives may be shared by many systems.
A tape drive or tape library is always controlled from the NovaNET
server. The setup is such that all devices are logically connected to the
NovaNET server although the server does not necessarily need physical
connectivity. The NovaNET server arbitrates the devices used so that only one
backup/restore operation can take place to a tape drive at any one time.
If one NovaNET client on the SAN is doing a backup to a tape drive, then other
NovaNET clients would need to use a different device or go into a queue until
the transfer is completed.
From an operational standpoint, the fact the device is SAN-attached is
transparent. NovaNET will always try to use a device that has local
attach or SAN connectivity thereby avoiding the network at all times. This
is done automatically and the user is not required to set up his backup jobs in
any special fashion.
SAN Serverless backup
What is it ?
SAN Serverless backup provides a method for transferring data directly from
the disk to the tape device without going through the host machine. This
works by having a SAN hub/router doing SCSI Copy commands. This takes a
physical block from the hard disk and copies to the tape.
The biggest benefit is reducing the amount of data the host has to process.
Normally data would be taken up to the host from the disk and back down
from the host to the drive. In SAN serverless backup the host only needs
to send each SCSI COPY initiator command; although this reduces that amount of
data to the host, the host is repeatingly sending the initiating COPY
This sort of backup is only appropriate to data where physical data copy is
appropriate. This is currently only applicable to filesystem
backups. With databases, data is backed up in a logical fashion which
means that data is retrieved via the database not by
going directly to the hard disk. For instance, Oracle backups are done
using RMAN, Informix using ONBAR, Sybase and MS SQL also have an API for
backups. None of these APIs supports direct physical access.
Serverless backup is not suitable for database
Unfortunately even filesystem backups via this method have limitations.
Firstly, because data is backed up on a disk block physical level, restores of
individual files and directories are difficult - in some cases impossible,
needing the whole partition to be restored. This also means that
incremental backups are seldom possible - forcing the user to backup the
complete filesystem every time.
Secondly, the technology requires a tight integration into various
filesystems which is normally done via "backdoor" methods as most filesystems do
not have APIs to support this. Some vendors do not allow this and interfering
with the filesystem in this way invalidates the vendor's support for the OS. To
further complicate matters OS vendors sometimes make minor changes to their
filesystems that do not affect traditional backup methods, but invalidate the
direct block access system.
One misconception is that, because the host is not involved, this is the
fastest method of doing backups. This is untrue. Having a host do a
backup means that the host can buffer a certain amount of information; this
means that if either the source (the disk) or the destination (the tape) should
slow down for brief period, the buffering will smooth out the data
transfer. This kind of buffering is not available in a Serverless
application where 8-32 Mb of buffering in a router/hub is inappropriate.
The main reason why benchmarks have shown an improvement is due to the
difference in doing raw block level backups against logical filesystem backups.
NovaNET 's position on SAN Serverless backups
NovaNET believes that SAN serverless backups are going to evolve into a
useful technology and the NovaNET product has provisions for its use.
Currently however, filesystems have not been designed to work with this
technology and the "back door" approach raises more problems than it
solves. Strategically NovaNET is ready for SAN serverless backup but is
waiting for filesystem technology to mature enough for these sorts of solutions
to be a realistic industry proposition.
About SAN Backup
SAN in Backup storage environment - What does it offer?
Fundamentally, SAN allows multiple machines connected to a SAN to share a
In a backup environment this gives the following advantages:
- Performance - Conventionally, when multiple machines use
a single tape library, they transfer the data across the network to a machine
that has connectivity to the tape devices; because each machine on the SAN can
directly communicate with the tape device, transfers speeds are equivalent to
having a device locally attached to the machine's SCSI bus.
- Can reduce cost - Where performance is critical, it is
necessary to have direct attachment to tape devices. This could mean
having several tape libraries connected to each machine; because SAN allows
multiple machines to share the same hardware, the storage can be consolidated
thereby saving cost. There is a careful balance that needs to be
achieved, as implementing SAN can be more costly than the hardware you are
trying to share.
- Flexible architecture - In a traditional environment some
machines have the centralized storage devices. If further expansion is
required, it is often quite complicated to try to redistribute the resources.
For the reason that SAN attached devices are shared, it is much easier to add
hardware and adjust which machines use which devices.
- Reduces network load - Although some sites have enough
network bandwidth to allow backups to occur across their network, the burden
on the network is often deemed unacceptable. SAN removes the load of the
SAN, especially in the backup storage environment, is
useful, it works and is ready