What is Drive Appearance

One of the more common, yet more tricky fundamental concepts in computing today is the concept of drive appearance or, in other words, something that appears to be a hard drive.  This may sound simple, and mostly it is, but it can be tricky.

First, what is a hard drive.  This should be simple.  We normally mean a traditional spinning disk Winchester device such have been made for decades in standard three and a half inch as well as two and a half inch form factors.  They contain platters that spin, a drive head that moves forward and backward and they connect using something like ATA or SCSI connectors.  Most of us can pick up a hard drive with our hands and be certain that we have a hard drive.  This is what we call the physical manifestation of the drive.

To the computer, though, it does not see the casing of the drive nor the connectors.  The computer has to look through its electronics and “see” the drive digitally.  This is very, very different from how humans view the physical drive.  To the computer, a hard drive appears as an ATA, SCSI or Fibre Channel device at the most basic physical level and are generally abstracted at a higher level as a block device.  This is what we would call a logical appearance, rather than a physical one.  For our purposes here, we will think of all of these drive interfaces as being block devices.  They do differ, but only slightly and not consequentially to the discussion.  What is important is that there is a standard interface or set of closely related interfaces that are seen by the computer as being a hard drive.

Another way to think of the logical drive appearance here is that anything that looks like a hard drive to the computer is something on which the computer format with a filesystem.  Filesystems are not drives themselves, but require a drive on which to be placed.

The concept of the interface is the most important one here.  To the computer, it is “anything that implements a hard drive interface” that is truly seen as being a hard drive.  This is both a simple as well as a powerful concept.

It is because of the use of a standard interface that we were able to take flash memory, attach it to a disk controller that would present it over a standard protocol (both SATA and SAS implementations of ATA and SCSI are common for this today) and create SSDs that look and act exactly like traditional Winchester drives to the computer yet have nothing physically in common with them.  They may or may not come in a familiar physical form factor, but they definitely lack platters and a drive head.  Looking at the workings of a traditional hard drive and a modern SSD we would not guess that they share a purpose.

This concept applies to many devices.  Obviously SD cards and USB memory sticks work in the same way.  But importantly, this is how partitions on top of hard drives work.  The partitioning system uses the concept of drive impression interface on one side to be able to be applied to a device, and on the other side it presents a drive impression interface to whatever wants to use it; normally a filesystem.  This idea of something that using the drive impression interface on both sides is very important.  By doing this, we get a uniform and universal building block system for making complex storage systems!

We see this concept of “drive in; drive out” in many cases.  Probably the best know is RAID.  A RAID system takes an array of hard drives, applies one of a number of algorithms to make the drives act as a team, and then present them as a single drive impression to the next system up the “stack.”  This encapsulation is what gives RAID its power: systems further up the stack looking at a RAID array see literally a hard drive.  They do not see the array of drives, they do not know what is below the RAID.  They just see the resulting drive(s) that the RAID system present.

Because a RAID system takes an arbitrary number of drives and presents them as a standard drive we have the theoretical ability to layer RAID as many times as we want.  Of course this would be extremely impractical to do to any great degree.  But it is through this concept that nested RAID arrays are possible.   For example, if we had many physical hard drives split into pairs and each pair in a RAID 1 array.  Each of those resulting arrays gets presented as a single drive.  Each of those resulting logical drives can be combined into another RAID array, such as RAID 0.  Doing this is how RAID 10 is built.  Going further we could take a number of RAID 10 arrays, present them all to another RAID system that puts them in RAID 0 again and get RAID 100 and so forth indefinitely.

Similarly the logical volume layer uses the same kind of encapsulation as RAID to work its magic.  Logical Volume Managers, such as LVM on Linux and Dynamic Disks on Windows, sit on top of logical disks and provide a layer where you can do powerful management such as flexibly expanding devices or enabling snapshots, and then present logical disks (aka drive impression interface) to the next layer of the stack.

Because of the uniform nature of drive impressions the stack can happen in any order.  A logical volume manager can sit on top of RAID, or RAID can sit on top of a logical volume manager and of course you can skip or the other or both!

The concept of drive impressions or logical hard drives is powerful in its simplicity and allows us great potential for customizing storage systems however we need to make them.

Of course there are other uses of the logical drive concept as well.  One of the most popular and least understood is that of a SAN.  A SAN is nothing more than a device that takes one or more physical disks and presents them as logical drives (this presentation of a logical drive from a SAN is called a LUN) over the network.  This is, quite literally, all that a SAN is.  Most SANs will incorporate a RAID layer and likely a logical volume manager layer before presenting the final LUNs, or disk impressions, to the network, but that is not required to be a SAN.

This means, of course, that multiple SAN LUNs can be combined in a single RAID or controlled via a logical volume layer.  And of course it means that a SAN LUN, a physical hard drive, a RAID array, a logical volume, a partition…. can all be formatted with a filesystem as they are all different means of achieving the same result.  They all behave identically.  They all share the drive appearance interface.

To give a real world example of how you would often see all of these parts come together we will examine one of the most common “storage stacks” that you will find in the enterprise space.  Of course there are many ways to build a storage stack so do not be surprised if yours is different.  At the bottom of the stack is nearly always physical hard drives, which could include solid state drives.  This are located physically within a SAN.  Before leaving the SAN the stack will likely include the actual storage layer of the drives, then a RAID layer combining those drives into a single entity.  Then a logical volume layer to allow for features like growth and snapshots.  Then there is the physical demarcation between the SAN and the server which is presented as the LUN.  The LUN then has a logical volume manager applies to it on the server / operating system side of the demarcation point.  Then on top of that LUN is a filesystem which is our final step as the filesystem does not continue to present a drive appearance interface but a file interface, instead.

Understanding drive appearance, or logical drives, and how these allows components to interface with each other to build complex storage subsystems is a critical building block to IT understanding and is widely applicable to a large number of IT activities.

Buyers and Sellers Agents in IT

When dealing with real estate purchases, we have discrete roles defined legally as to when a real estate agent represents the seller or when they represent the buyer.  Each party gets clear documentation as to how they are being represented.  In both cases, the agent is bound by honesty and ethical limitations, but beyond that their obligations are to their represented party.

Outside of the real estate world, most of us do not deal with buyer’s agents very often.  Seller’s agents are everywhere, we just call them salespeople.  We deal with them at many stores and they are especially evident when we go to buy something large, like a car.

In business, buyer’s agents are actually pretty common and actually come in some interesting and unspoken forms.  Rarely does anyone actually talk about buyer’s agents in business terms, mostly because we are not talking about buying objects but about buying solutions, services or designs.  Identifying buyer’s and seller’s agents alone can become confusing and, often, companies may not even recognize when a transaction of this nature is taking place.

We mostly see the engagement of sellers – they are the vendors with products and services that they want us to purchase.  We can pretty readily identify the seller’s agents that are involved.  These include primarily the staff of the vendor itself and the sales people (which includes pre-sales engineering and any “technical” resource that gets compensation by means of the sale rather than being explicitly engaged and remunerated to represent your own interests) of the resellers (resellers being a blanket term for any company that is compensated for selling products, services or ideas that they themselves do not produce; this commonly includes value added resellers and stores.)  The seller’s side is easy.  Are they making money by somehow getting me to buy something?  If so… seller’s agent.

Buyer’s agents are more difficult to recognize.  So much so that it is common for businesses to forget to engage them, overlook them or confuse seller’s agents for them.  Sadly, outside of real estate, the strict codes of conduct and legal oversight do not exist and ensuring that seller’s agent is not engaged mistakenly where a buyer’s agent should be is purely up to the organization engaging said parties.

Buyer’s agents come in many forms but the most common, yet hardest to recognize, is the IT department or staff, themselves.  This may seem like a strange thought, but the IT department acts as a technical representative of the business and, because they are not the business themselves directly, an emotional stop gap that can aid in reducing the effects of marketing and sales tactics while helping to ensure that technical needs are met.  The IT team is the most important buyer’s agent in the IT supply chain and the last line of defense for companies to ensure that they are engaging well and getting the services, products and advice that they need.

Commonly  IT departments will engage consulting services to aid in decision making. The paid consulting firm is the most identifiable buyer’s agent in the process and the one that is most often skipped (or a seller’s agent is mistaken for the consultant.)  A consultant is hired by, paid by and has an ethical responsibility to represent the buyer.  Consultants have an additional air gap that helps to separate them from the emotional responses common of the business itself.  The business and its internal IT staff are easily motivated by having “cool solutions” or expensive “toys” or can be easily caused to panic through good marketing, but consultants have many advantages.

Consultants have the advantage that they are often specialists in the area in question or at least spend their time dealing with many vendors, resellers, products, ideas and customer needs.  They can more easily take a broad view of needs and bring a different type of experience to the decision table.

Consultants are not the ones who, at the end of the day, get to “own” the products, services or solutions in question and are generally judged on their ability to aid the business effectively.  Because of this they have a distinct advantage in being more emotionally distant and therefore more objective in deciding on recommendations.  The coolest, newest solutions have little effect on them while cost effectiveness and business viability do.  More importantly, consultants and internal IT working together provide an important balancing of biases, experience and business understandings that combine the broad experience across many vendors and customers of the one, and the deep understanding of the individual business of the other.

One can actually think of the Buyer’s and Seller’s Agent system as a “stack”.  When a business needs to acquire new services, products or to get advice, the ideal and full stack would look something like this: Business > IT Department > ITSP/Consultants <> Value Added Reseller < Distributor < Vendor.  The <> denotes the reflection point between the buyer’s side and the seller’s side.  Of course, many transactions will not involve and should not involve the entire stack.  But this visualization can be effective in understanding how these pieces are “designed” to interface with each other.  The business should ideally get the final options from IT (IT can be outsourced, of course), IT should interface through an ITSP consultant in many cases, and so forth.  An important part of the processes is keeping actors on the left side of the stack (or the bottom) from having direct contact with those high up in the stack (or on the right) because this can short circuit the protections that the system provides allowing vendors or sales staff to influence the business without the buyer’s agents being able to vet the information.

Identifying, understanding and leveraging the buyer’s and seller’s agent system is important to getting good, solid advice and sales for any business and is widely applicable far outside of IT.

The Emperor’s New Storage

We all know the story of the Emperor’s New Clothes.  In Hans Christian Anderson’s telling of the classic tale we have some unscrupulous cloth vendors who convince the emperor that they have clothes made from a fabric with the magical property of only being visible to people who are fit for their positions.  The emperor, not being able to see the clothes, decides to buy them because he fears people finding out that he cannot see them.  Everyone in the kingdom pretends to see them as well – all sharing the same fear.  It is a brilliant sales tactic because it puts everyone on the same team: the cloth sellers, the emperor, the people in the street all share a common goal that requires them to all maintain the same lie.  Only when a little boy who cares naught about his status in society but only about the truth points out that the emperor is naked is everyone free to admit that they don’t see the clothes either.

And this brings us to the storage market today.  Today we have storage vendors desperate to sell solutions of dubious value and buyers who often lack the confidence in their own storage knowledge to dare to question the vendors in front of management or who simply have turned to vendors to make their IT decisions on their behalf.  This has created a scenario where the vendor confidence and industry uncertainty has engendered market momentum causing the entire situation to snowball.  The effect is that using big, monolithic and expensive storage systems is so accepted today that often systems are purchased without any thought at all.  They are essentially a foregone conclusion!

It is time for someone to point at the storage buying process and declare that the emperor is, in fact, naked.

Don’t get me wrong.  I certainly do not mean to imply that modern storage solutions do not have value.  Most certainly they do.  Large SAN and NAS shared storage systems have driven much technological development and have excellent use cases.  They were not designed without value, but they do not apply to every scenario.

The idea of the inverted pyramid design, the overuse of SANs where they do not apply, came about because they are high profit margin approaches.  Manufacturers have a huge incentive to push these products and designs because they do much to generate profits.  SANs are one of the most profit-bearing products on the market.  This, in turn, incentivizes resellers to push SANs as well, both to generate profits directly through their sales but also to keep their vendors happy.  This creates a large amount of market pressure by which everyone on the “sales” side of the buyer / seller equation has massive pressure to convince you, the buyer, that a SAN is absolutely necessary.  This is so strong of a pressure, the incentives so large, that even losing the majority of potential customers in the process is worth it because the margins on the one customer that goes with the approach is generally worth losing many others.

Resellers are not the only “in between” players with incentive to see large, complex storage architectures get deployed.  Even non-reseller consultants have an incentive to promote this approach because it is big, complex and requires, on average, far more consulting and support than do simpler system designs.  This is unlikely to be a trivial number.  Instead of a ten hour engagement, they may win a hundred hours, for example, and for consultants those hours are bread and butter.

Of course, the media has incentive to promote this, too.  The vendors provide the financial support for most media in the industry and much of the content.  Media outlets want to promote the design because it promotes their sponsors and they also want to talk about the things that people are interested in and simple designs do not generate a lot of readership.  The same problems that exist with sensationalist news: the most important or relevant news is often skipped so that news that will gather viewership is shown instead.

This combination of factors is very forceful.  Companies that look to consultants, resellers and VARs, and vendors for guidance will get a unanimous push for expensive, complex and high margin storage systems.  Everyone, even the consultants who are supposed to be representing the client have a pretty big incentive to let these complex designs get approved because there is just so much money potentially sitting on the table.  You might get paid one hour of consulting time to recommend against overspending, but might be paid hundreds of hours for implementing and supporting the final system.  That’s likely tens of thousands of dollars difference, a lot of incentive, even for the smallest deployments.

This unification of the sales channel and even the front line of “protection” has an extreme effect.  Our only real hope, the only significant one, for someone who is not incentivized to participate in this system is the internal IT staff themselves.  And yet we find very rarely that internal staff will stand up to the vendors on these recommendations or even produce them themselves.

There are many reasons why well intentioned internal IT staff (and even external ones) may fail to properly assess needs such as these.  There are a great many factors involved and I will highlight some of them.

  • Little information in the market.  Because no company makes money by selling you less, there is almost no market literature, discussions or material to assist in evaluating decisions.  Without direct access to another business that has made the same decision or to any consultants or vendors promoting an alternative approach, IT professionals are often left all alone.  This lack of supporting experience is enough to cause adequate doubt to squash dissenting voices.
  • Management often prefers flashy advertising and the word of sales people over the opinions of internal staff.  This is a hard fact, but one that is often true.  IT professionals often face the fact that management may make buying decisions without any technical input whatsoever.
  • Any bid process immediately short circuits good design.  A bid would have to include “storage” and SAN vendors can easily bid on supplying storage while there is no meaningful way for “nothing” to bid on it.  Because there is no vendor for good design, good design has no voice in a bidding or quote based approach.
  • Lack of knowledge.  Often dealing with system architecture and storage concerns are one off activities only handled a few times over an entire career.  Making these decisions is not just uncommon, it is often the very first time that it has ever been done.  Even if the knowledge is there, the confidence to buck the trend easily is not.
  • Inexperience in assessing risk and cost profiles.  While these things may seem like bread and butter to IT management, often the person tasked with dealing with system design in these cases will have no training and no experience in determining comparative cost and risk in complex systems such as these.  It is common that risk goes unidentified.
  • Internal staff often see this big and costly purchase as a badge of honour or a means to bragging rights.  Excited to show off how much they were able to spend and how big their new systems are.  Everyone loves gadgets and these are often the biggest, most expensive toys that we ever touch in our industry.
  • Internal staff often have no access to work with equipment of this type, especially SANs.  Getting a large storage solution in house may allow them to improve their resume and even leverage the experience into a raise or, more likely, a new job.
  • Turning to other IT professionals who have tackled similar situations often results in the same advice as from sales people.  This is for several reasons.  All of the reasons above, of course, would have applied to them plus one very strong one – self preservation.  Any IT professional that has implemented a very costly system unnecessarily will have a lot of incentive to state that they believe that the purchase was a good one.  Whether this is irrational “reverse rationalization” – the trait where humans tend to apply ration to a decision that lacked ration when originally made, because they fear that their job may be in jeopardy if it was found out what they had done or because they have not assessed the value of the system after implementation; or even possibly because their factors were not the same as yours and the design was applicable to their needs.

The bottom line is that basically everyone, no matter what role they play, from vendors to sales people to those that do implementation and support to even your friends in similar job roles to strangers on Internet forums, all have big incentives to promote costly and risky storage architectures in the small and medium business space.  There is, for all intents and purposes, no one with a clear benefit for providing a counter point to this marketing and sales momentum.  And, of course, as momentum has grown the situation becomes more and more entrenched with people even citing the questioning of the status quo and asking critical questions as irrational or reckless.

As with any decision in IT, however, we have to ask “does this provide the appropriate value to meet the needs of the organization?”  Storage and system architectural design is one of the most critical and expensive decisions that we will make in a typical IT shop.  Of all of the things that we do, treating this decision as a knee-jerk, foregone conclusion without doing due diligence and not looking to address our company’s specific goals could be one of the most damaging that we make.

Bad decisions in this area are not readily apparent.  The same factors that lead to the initial bad decisions will also hide the fact that a bad decision was made much of the time.  If the issue is that the solution carries too much risk, there is no means to determine that better after implementation than before – thus is the nature of risk.  If the system never fails we don’t know if that is normal or if we got lucky.  If it fails we don’t know if this is common or if we were one in a million.  So observation of risk from within a single implementation, or even hundreds of implementations, gives us no statistically meaningful insight.  Likewise when evaluating wasteful expenditures we would have caught a financial waste before the purchase just as easily as after it.  So we are left without any ability for a business to do a post mortem on their decision, nor is there an incentive as no one involved in the process would want to risk exposing a bad decision making process.  Even companies that want to know if they have done well will almost never have a good way of determining this.

What makes this determination even harder is that the same architectures that are foolish and reckless for one company may be completely sensible for another.  The use of a SAN based storage system and a large number of attached hosts is a common and sensible approach to controlling costs of storage in extremely large environments.  Nearly every enterprise will utilize this design and it normally makes sense, but is used for very different reasons and goals than apply to nearly any small or medium business.  It is also, generally, implemented somewhat differently.  It is not that SANs or similar storage are bad.  What is bad is allowing market pressure, sales people and those with strong incentives to “sell” a costly solution to drive technical decision making instead of evaluating business needs, risk and cost analysis and implementing the right solution for the organization’s specific goals.

It is time that we, as an industry, recognize that the emperor is not wearing any clothes.  We need to be the innocent children who point, laugh and question why no one else has been saying anything when it is so obvious that he is naked.  The storage and architectural solutions so broadly accepted benefit far too many people and the only ones who are truly hurt by them (business owners and investors) are not in a position to understand if they do or do not meet their needs.  We need to break past the comfort provided by socially accepted plausible deniability or understanding, or culpability for not evaluating.  We must take responsibility for protecting our organizations and provide solutions that address their needs rather than the needs of the sales people.

 

For more information see: When to Consider a SAN and The Inverted Pyramid of Doom

Disaster Recovery Planning with Existing Platform Equipment

Disaster Recovery planning is always difficult, there are so many factors and “what ifs” that have to be considered and investing too much in the recovery solution can itself become a  bit of a disaster.  A factor that is often overlooked in DR planning is that: in the event of a disaster you are generally able and very willing to make compromises where needed because a disaster has already happened.  It is triage time, not business as usual.

Many people immediately imagine that if you need capacity and performance of X for your live, production systems that you will need X as well for your disaster recovery systems.  In the real world, this is rarely true, however.  In the event of a disaster you can, with rare exception, work with lower performance and limit system availability to just the more critical systems and many maintenance operations, which often includes archiving systems, are suspended until full production is restored.  This means that your disaster recovery system can often be much smaller than your primary production systems.

Disaster recovery systems are not investments in productivity, they are hedges against failure and need to be seen in that light.  Because of this it is a common and effective strategy to approach the DR system needs more from a perspective of being “adequate” to maintain business activities while not enough to necessarily do so comfortably or transparently.  If a full scale disaster hits and staff have to deal with sluggish file retrieval, slower than normal databases or hold off on a deep BI analysis run until the high performance production systems are restored, few people will complain.  Most workers and certainly more business decision makers can be very understanding that a system is in a failed state and that they may need to help carry on as best as they can until full capacity is restored.

With this approach in mind, it can be an effective strategy to re-purpose older platforms for use at Disaster Recovery sites when new platforms are purchased and implemented for primary production usage.  This can create a low cost and easily planned around “DR pipeline” where the DR site always has the capacity of your “last refresh” which, in most DR scenarios, is more than adequate.  This can be a great way to make use of equipment that otherwise might either be scrapped outright or might tempt itself into production re-deployment by invoking a “sunk cost” emotional response that, in general, we want to avoid.

The sunk cost fallacy is a difficult one to avoid.  Already owning equipment makes it very easy to feel that deploying it again, even when a newly designed system is being implemented, outside of the system designs and specifications is useful or good.  And there are cases where this might be true, but most likely it is not.  But just as we don’t want to become overly emotionally attached to equipment just because we have already paid for it, we also don’t want to ignore the value in the existing equipment that we already own.  This is where a planned pipeline into a Disaster Planning scenario can leverage what we have already invested in a really great way in many cases.  We do have to remember that this is likely very useful equipment with a lot of value left in it, if we just know how to use it properly to meet our existing needs.

A strong production to disaster recovery platform migration planning process can be a great way to lower budgetary spending while getting excellent disaster recovery results.