Wir möchten Ihnen gern unser besonderes Schulungsangebot für das erste Quartal 2010 unterbreiten. Das Unternehmen CA führt in unserm Hause ein erweitertes Training für die Software CA ARCserve durch. Der Inhalt der Schulung richtet sich insbesondere an Administratoren, die ARCserve in einer SAN-Umgebung oder alternativ in einer NAS Umgebung betreiben. Alle Informationen zur Schulung erhalten Sie bei der SIGMA Chemnitz GmbH.

Storage Basics: Storage Area Networks

Many IT organizations today are scratching their heads debating whether the advantages of implementing a SAN solution justify the associated costs. Others are trying to get a handle on today’s storage options and whether SAN is simply Network Attached Storage spelled backwards. In this article, I introduce the basic purpose and function of a SAN and examine its role in modern network environments. I also look at how SANs meet the network storage needs of today’s organizations and answer the question, could a SAN be right for you.

Peel away the layers of even the most complex technologies and you are likely to find that they provide the most basic of functions. This is certainly true of storage area networks (SANs). Behind the acronyms and revolutionary headlines, lies a technology designed to provide a way of offering one of the oldest of network services, that of making access to data storage devices available to clients.

In very basic terms, a SAN can be anything from two servers on a network accessing a central pool of storage devices to several thousand servers accessing many millions of megabytes of storage. Conceptually, a SAN can be thought of as a separate network of storage devices physically removed from, but still connected to, the network. SANs evolved from the concept of taking storage devices, and therefore storage traffic, off the LAN and creating a separate back-end network designed specifically for data.

SANs represent the evolution of data storage technology to this point. Traditionally, on client server systems, data was stored on devices either inside or directly attached to the server. Next in the evolutionary scale came Network Attached Storage (NAS) which took the storage devices away from the server and connected them directly to the network. SANs take the principle one step further by allowing storage devices to exist on their own separate network and communicate directly with each other over very fast media. Users can gain access to these storage devices through server systems which are connected to both the LAN and the SAN.

This is in contrast to the use of a traditional LAN for providing a connection for server-storage, a strategy that limits overall network bandwidth. SANs address the bandwidth bottlenecks associated with LAN based server storage and the scalability limitations found with SCSI bus based implementations. SANs provide modular scalability, high-availability, increased fault tolerance and centralized storage management. These advantages have led to an increase in the popularity of SANs as they are quite simply better suited to address the data storage needs of today’s data intensive network environments.

The advantages of SANs are numerous, but perhaps one of the best examples is that of the serverless backup (also commonly referred to as 3rd Party Copying). This system allows a disk storage device to copy data directly to a backup device across the high-speed links of the SAN without any intervention from a server. Data is kept on the SAN, which means the transfer does not pollute the LAN, and the server processing resources are still available to client systems.

SANs are most commonly implemented using a technology called Fibre channel (yes, that’s fibre with an ‘re’, not an ‘er’). Fibre Channel is a set of communication standards developed by the American National Standards Institute (ANSI). These standards define a high-performance data communications technology that supports very fast data rates (over 2Gbps). Fibre channel can be used in a point-to-point configuration between two devices, in a ‘ring’ type model known as an arbitrated loop, and in a fabric model.

Devices on the SAN are normally connected together through a special kind of switch, called a Fibre Channel switch, which performs basically the same function as a switch on an Ethernet network, in that it acts as a connectivity point for the devices. Because Fibre channel is a switched technology, it is able to provide a dedicated path between the devices in the fabric so that they can utilize the entire bandwidth for the duration of the communication.

The storage devices are connected to Fibre Channel switch using either multimode or single mode fiber optic cable. Multimode for short distances (up to 2 kilometers), single mode for longer. In the storage devices themselves, special fiber channel interfaces provide the connectivity points. These interfaces can take the form of built in adapters, which are commonly found in storage subsystems designed for SANs, or can be interface cards much like a network card, which are installed into server systems.

So, the question that remains is this. Should you be moving away from your current storage strategy and towards a SAN? The answer is not a simple one. If you have the need to centralize or streamline your data storage then a SAN may be right for you. There is, of course, one barrier between you and storage heaven, and that’s money. While SANs remain the domain of big business, the price tag’s of SAN equipment is likely to remain at a level outside the reach of small or even medium sized businesses. As the prices fall, however, SANs will find their way into organizations of all sizes, including, if you want, yours.

With their recent acquisition of Data Domain, some people at EMC have become table thumping experts overnight on why you it’s absolutely imperative that you backup to Data Domain boxes as disk backup over NAS, rather than a fibre-channel connected VTL.

Their argument seems to come from the numbers – the wrong numbers.

The numbers constantly quoted are number of sales of disk backup Data Domain vs VTL Data Domain. That is, some EMC and Data Domain reps will confidently assert that by the numbers, a significantly higher percentage of Data Domain for Disk Backup has been sold than Data Domain with VTL. That’s like saying that Windows is superior to Mac OS X because it sells more. Or to perhaps pick a little less controversial topic, it’s like saying that DDS is better than LTO because there’s been more DDS drives and tapes sold than there’s ever been LTO drives and tapes.

I.e., an argument by those numbers doesn’t wash. It rarely has, it rarely will, and nor should it. (Otherwise we’d all be afraid of sailing too far from shore because that’s how it had always been done before…)

Let’s look at the reality of how disk backup currently stacks up in NetWorker. And let’s preface this by saying that if backup products actually started using disk backup properly tomorrow, I would be the first to shout “Don’t let the door hit your butt on the way out” to every VTL on the planet. As a concept, I wish VTLs didn’t have to exist, but in the practical real world, I recognise their need and their current ascendency over ADV_FILE. I have, almost literally at times, been dragged kicking and screaming to that conclusion.

Disk Backup, using ADV_FILE type devices in NetWorker:

• Can’t move a saveset from a full disk backup unit to a non-full one; you have to clear the space first.
• Can’t simultaneously clone from, stage from, backup to and recover from a disk backup unit. No, you can’t do that with tape either, but when disk backup units are typically in the order of several terabytes, and virtual tapes are in the order of maybe 50-200 GB, that’s a heck of a lot less contention time for any one backup.
• Use tape/tape drive selection algorithms for deciding which disk backup unit gets used in which order, resulting in worst case capacity usage scenarios in almost all instances.
• Can’t accept a saveset bigger than the disk backup unit. (It’s like, “Hello, AMANDA, I borrowed some ideas from you!”)
• Can’t be part-replicated between sites. If you’ve got two VTLs and you really need to do back-end replication, you can replicate individual pieces of media between sites – again, significantly smaller than entire disk backup units. When you define disk backup units in NetWorker, that’s the “smallest” media you get.
• Are traditionally space wasteful. NetWorker’s limited staging routines encourages clumps of disk backup space by destination pool – e.g., “here’s my daily disk backup units, I use them 30 days out of 31, and those over there that occupy the same amount of space (practically) are my monthly disk backup units, I use them 1 day out of 31. The rest of the time they sit idle.”
• Have poor staging options (I’ll do another post this week on one way to improve on this).

If you get a table thumping sales person trying to tell you that you should buy Data Domain for Disk Backup for NetWorker, I’d suggest thumping the table back – you want the VTL option instead, and you want EMC to fix ADV_FILE.

Honestly EMC, I’ll lead the charge once ADV_FILE is fixed. I’ll champion it until I’m blue in the face, then suck from an oxygen tank and keep going – like I used to, before the inadequacies got too much. Until then though, I’ll keep skewering that argument of superiority by sales numbers.

What’s more American than spending Thanksgiving at a historical site? Four score and a few years ago my dear friend Jessica drove from Los Angeles to meet me in San Diego where I was meeting my father and his girlfriend for Thanksgiving dinner. Starwood had a four night special at several hotels in the area. At first I chose the Westin, where I was promised a suite. However, at the very last minute I decided to try something new and booked four nights at The U.S. Grant. The property was newly rehabbed and was all the talk on the blogosphere. The room I choose had a jacuzzi.

When I got off the plane I realized I left my toiletry bag at home! I called the hotel prior to ask for assistance. At the hotel I entered through a side door which through me for a loop. The decor was classic but plush. I asked for an upgrade and they laughed and handed me my room keys. Again, being a Starwood property I was entitled to an upgrade.

As I slid my room key my excitement peaked. Then BAM! My room was the size closet. The bed and flatscreen TV were great but thats all that seemed to fit in the room. I called the front desk. Again, they claimed I had to pay for an upgrade. I know the hotel was empty, it was very obvious they didn’t know who they were messing with. Realizing sometimes you can’t win I decided to check out this “wonder-tub”. The jets were intense and the water changed pretty colors. It was like a disco in a jacuzzi. This is what I was paying for. Then I saw there amenities. They were from some British bath company I have never heard of. I strolled downstairs to ask the concierge if they wouldn’t mind getting me some Bliss amenities from the W Hotel around the corner. Both hotels were Starwood so I figured this wouldn’t be a problem. They said “yes”. Days went by and nothing happened.

After a night of partying with Jessica at a MSTRKFT show we decided to buy our own booze and keep the party going. At one point I literally fell over this random chair almost knocking over the flatscreen. It was a good thing the bed was in reach. In fact I could lay in bed and touch anything in the room. We took some videos and eventually passed out.

Soon we realized everyone at the hotel was over 60 years old. We did not fit in. For what we were paying we could of had our suite at the Westin across the street where we stayed once before or a normal room at the W Hotel. The looks we were getting mirrored the same from the move “Pretty Women”. Even the staff was awful.

I decided to seek out the GM. I explained to him that I have the smallest room. The concierge never kept their one promise I asked and the staff was terribly rude. I asked him for a scissors and threatened to cut my gold card in front of a large group of guests checking in. He broke down and apologized. Just then Jessica strutted over in her heels and short skirt. There was an awkward moment. The GM looked at me and stated “I will give you 20,000 Starpoints for your troubles.” I dropped the scissors and walked away.

FYI – The U.S. Grant ended up being featured on an episode of “The Real Housewives of Orange County”.

2 mints on the pillow when all was said and done.

Fotos por: Pedro Guerra.                               Publicación por: Michel de León.