Disk Drive Types

Intro
I am writing this because of the amount of questions I get from SMB (Small to Medium Business) customers about why there are so many different types of disks and one even asked me, "why doesn't Microsoft standardize on a disk type" (please do not take offense to the example if you are reading this).
Preface
The explanations here are provided as an overview and are intended to be fairly simplistic to allow a greater audience to understand the differences in disk drives. Storage design and architecture can be an extremely complex topic. There are many factors that go into designing a corporate storage infrastructure. Items such as, but not limited to the following: desired performance, footprint or space consumed, uptime, budget, disaster recovery, etc.   
Microsoft
First I will tackle the Microsoft question. Microsoft is a software company not a hardware company (I know they do make some hardware, but it is mainly for the home consumer market). Since they are the 10 ton guerilla in the Operating System arena they do have some input into disks, but they do not set the standards. They take advantage of what is available in the market and work with Storage manufacturers to ensure hardware works with their Operating System (i.e. the windows family). The big boys in storage are Hitachi, Seagate, Western Digital, Toshiba and IBM.
Terms Commonly Used with Disk Drives

• Platter - this refers to the physical platter inside the disk enclosure, all data is read from and written to the disk platter. 
  
• RPM - this refers to the revolutions per minute the disk platter spins. The faster the platter spins the faster the disk head can read and write information to the disk. Disk speeds are available anywhere from 5,400 to 15,000 RPMs
• CACHE - this refers to the buffer mechanism that transfers data from a relatively fast area of the computer (memory or RAM) to the relatively slower areas of the computer (the disk platter). A larger cache will help speed up a computer by buffering information and allowing the computer to continue writing data as opposed to waiting for the data to be written to the platter. Think of it a little like a funnel with a large reservoir allowing you to pour liquid into a container continously as opposed to a little at a time.
• Interface - this refers to the type of connector used to physically connect a disk to the computer most disk types are named based on their interface type
• NAS - Network attached storage, meaning the data is accessed via a network sharing mechanism like a windows share (SMB) or NFS
• SAN - Storage Area Network this is a high end array of disks, that is managed from a central set of software. SANs offer greater management capabilities and superioir performance over other types of storage. This gives business greater control over their data and teriffic disaster recovery capabilities.
  

Older Disk Types
Just as every other technology changes and sometimes improves over time so do disk drives. Take the TV industry as an example; Plasma, Projection, LCD, etc. For many years there were basically 2 major disk types both of which are being phased out for newer, smaller and faster disks.

• IDE (used for desktops and low end servers)
• SCSI -Small Computer Systems Interface (used for servers and high end desktops or workstations)

IDE was used where performance and MTBF (mean time between failure) was not as critical as the cost to purchase; desktops and laptops. Max RPMs are generally limited to 7200 (I have read about 10k but have never personally seen one)
SCSI was used primarily where performance and MTBF was more important than cost; servers, SANs, workstations. Max RPMs as high as 15k
Newer Standards
Although there are more disk types than I am listing I am only going to cover the 4 major players

• SATA 
• Fiber Channel 
• SAS 
• Solid State

SATA is emerging as the defacto standard for desktops and laptops. There are different class SATA drives that offer better MTBF and performance than others, the ones used in desktops are typically part of the lower end classes and seem to be giving SATA a bad rap in the computer industry. Max RPMs for SATA is 10k but typically people will use a 7200 or 5400 rpm drive. There are several reasons for this becoming a standard and some of those are not obvious to anyone outside the hardware industry.

• Transfer speeds are much faster than IDE (meaning data can be read from and written to the disk more quickly via the interface cable connecting the drive to the computer itself)
• Because IDE is going away you will see larger disk drives in SATA than IDE
• Because SATA uses a much smaller cable and connector than IDE it consumes a smaller total footprint allowing better airflow throughout the machine (this gives a lot of advantage to the performance and MTBF of the machine as a whole). 
•  Easier to install, because a lack of jumper settings that were typical of IDE drives.
• I have read they have a higher MTBF than IDE, but this is not evident from what I have seen.
• Newer SATA drives can offer greater cache sizes than IDE
  

Fiber Channel (FC) is and has been the standard in servers and SANS for quite some time. FC drives are typically more reliable than SATA and IDE (I don't have enough experience with SAS to say yet). FC drives also offer much higher speeds than SATA drives, not only from the cables that are used to connect the drives but also through the RPMs they deliver. Although SATA drives have been built to sustain 15k they are rare and I would think the MTBF for those drives would be much lower than FC or SAS drives. Fiber channel connected drives use light to transfer data between devices allowing for very fast transfers, an externally connected FC array of disks will typically provide much better performance than an internally connected SATA disk. FC is firmly entrenched in the majority of enterprise SANs and many enterprises have invested an enormous amount of money in their SAN infrastructure which means FC will be around for the foreseeable future. (See topic below comparing SAS to FC)
SAS (Serial Attached SCSI) is the new kid on the block for mid to high end disk drives. SAS is quickly becoming the disk type of choice for servers, high end workstations, NAS devices and mid range SANs. Many experts believe that SAS will eventually take over the number one spot in SAN disks as well, but there are currently limiting factors that will prevent that from happening in the near future. (See topic below comparing SAS to FC). Max RPMs for SAS is currently 15k.
Solid State Drives (SSD) are the newest rave and rightly so. They don't have moving parts which means the MTBF should be extremely high it also means they do not make noise. Although a lot is being said about the new SSD it is not a new technology, SSD emerged as auxillary memory units during the era of vacuum tube computers where replaced by cheaper drum storage units. Cray, Amdahl and IBM used them as far back as the 70's for specialty computers, but it was very expensive and rarely used. SSDs have extremely fast reads and transfer rates of up to 3 Gbits/s, but delivering better performance because of the lack of a spinning disk. Currently it is still expensive to implement and the sizes are typically small. Toshiba will begin manufacturing a 512 gb SSD this quarter (q1 2009). IBM has announced it tested a 4 tb SSD but not much is known about it. This will continue to be a niche device where speed is of the utmost importance. 

SAS vs. FC
Since it seems for the enterprise the big question is what do I go with FC or SAS, I will list some of the differences.

• SAS spindle speeds are comparable to FC
• SAS transfer rates are slower, FC offers 4 Gbits/s while SAS currently only offers 3 Gbits/s. 
• SAS is up to 50% cheaper to manufacture than FC meaning a lower entry cost
• SAS drives can be smaller (2.5" vs 3.5") and manufacturers claim that the smaller units consume less power.
• FC is more mature
• SAS is limited in the number host ports it can connect, making it difficult to use in larger SAN infrastructures. There are vendors making expanders to overcome this supporting thousands of connected devices.
• SAS is limited to an 8ft connection from its controller. A large 5 frame SAN will have a lot longer runs between the back planes making SAS a non player in that market for the time being. Future development will probably overcome this limitation though.
  

Summary
For desktop and home consumers SATA will continue to be the disk type of choice. Performance oriented individuals will start to use SAS and SSD in niche performance markets. For the SMB market SAS will be the disk type of choice for servers, NAS and SANs. Manufacturers have a large investment in FC and will likely continue to push FC as the disk type of choice for the large enterprise SANs and for the mean time keep the advancements of SAS slightly behind FC, much the same way IBM keeps the P series development slightly behind the mainframe (there is more money to be made on FC for the time being). Consumers will likely force the manufacturers hands over time as smaller players in the storage arena continue to advance the development of SAS. As the smaller players start to consume market space the larger guys like Hitachi and EMC will go balls to the wall to reclaim that space and provide SAS capabilities in the enterprise arrays.

I hope this was of use to some people trying to understand the amount of choices in disk technology.

Storage Trends

Fiber vs. iSCSI
SAS vs. SATA vs. Fiber vs. IDE vs. Solid State
4600 vs. 5400 vs. 7200 vs. 10k vs 15k

Do all of the above make you shake your head and think WHY are there so many choices? Things used to be so easy when all you had was IDE and SCSI drives available. But during those times people didn't expect subsecond response when they clicked on button, then again most business programs didn't have buttons.

I recently had an executive at fairly large company ask me why don't we standardize on things. This same executive asked me at different times, how to get faster response times, how to make a laptops battery last longer, how to make a smaller laptop, how to connect to more storage without adding more wiring and how he could take his video and music collection with him.

All  of the above figures in to the questions he asked.  In future posts I will start explaining the needs and uses of all of those options.

Luckier Today

My fiasco yesterday with my cart got a little better, after pulling out all of the burnt wiring I rewired the system, bypassing the switch to the hydraulic dump bed and I am now able to actually start the cart and drive it. The dump bed is stuck in the up position from yesterday, but I can either take the hydraulic pump out and lower the bed or attempt to reverse the polarity and see if it will come down until I can get a new 3 position switch for it.

Bad news is I can not find a used lift link for my tractor and it is going to cost me $225 dollars for a replacement. But this is better than the $500 - $800 I was forecasting last night. I am sure I can get the switch for the hyrdraulic lift under $25 so it looks like I am going to get away with only having to spend $250.

Sometimes things just don't go your way

Have you ever decided not to do some type of recreational activity simply because you didn't want to spend the money, then because you stayed at home ended up having to spend 5 times the amount that you would have spent? That happened to me on Sunday. I really enjoy shooting sporting clays, this is a shotgun sport that many call "golf with guns" (more on that in a latter post). Sunday I had one of my buddies try to get me to go with him to a Bird In Hand in Plains, GA. I told him I was going to skip because I didn't have the ammo and didn't want to spend the money on the round, buy ammunition and gas, so I thought I would do good and save that $75 and stay at home.

Wrong decision.

I drove my "Golf Cart" (this is one of the converted types with mud tires, lift kit and hydraulic dump bed I use for maintenance chores around my place) over to my neighbors house to check on them. While I was there one of the kids asked if he could take my cart out to check his deer feeders. I didn't see any harm and said sure.

Wrong Decison again

About 1 and half hours later the kid walked back to the house saying he couldn't get the cart started. I thought maybe he ran it out of gas, so we walked back to my house so that we could get my tractor to tow the buggy back to the house if I couldn't get it started.

Wrong Decision again

We went out to where the buggy was sitting, I was relieved to see it wasn't buried in the mud. I tried to start the cart, and it wouldn't even turn over, I thought it must be a loose wire or something, I have had that happen in the past while traveling through wooded areas. I tried to lift the hydraulic dump bed to get to the engine area and the switch did not respond, I also noticed it was stuck in the down position. I said fine and lifted the seat up to get to the battery and electrical connections and I was horrified to see a lot of wires burned beyond recognition. It appeared that either he had his leg sitting on the down switch to the dump bed and he didn't know that the loud whine the hydraulics were making meant something was wrong so he kept driving, after all he had to check those deer feeders. (To my knowledge he has never killed a deer there, he tends to go out and get too wasted to actually go hunting the next morning.) I held my temper and hooked the 3 point hitch lift bar of the tractor to a tow chain connected the cart so that we could tow it back home and I could see how much damage was done.

Wrong Decision yet again

When I turned the tractor and started pulling the cart I heard a loud pop, no it wasn't the chain and there was not a bloody corpse of the boy behind me, but the lift arm of the tractor was now lying in the mud behind me. Because in my haste and frustration I forgot to put the pin in the sway bar and the lift arm broke in half. I then hooked the chain to the frame of the tractor and pulled it back to my house.

Now after trying to save $75 I am faced with $230 worth of broken tractor parts and if I am lucky probably $300 - $500 worth of damage to my cart.

So saving $75 just cost me $800. Moral of the story is if you get a chance to go do your favorite hobby go play. It may just save you a grand and make you feel a hell a lot better than allowing a kid to tear up your tools that you have to replace!

Constitutional Two Faces

Is it not ironic that the same people who rightfully protested President Bush's flagrant disregard of our constitutional privacy laws will willing stand by and even suggest that the new administration enact laws that are so strict that our 2nd Amendment rights are in jeopardy.

Some of those proposed laws are listed below:

• A 400% TAX on ammunition (the price of ammo is already sky rocketing; 6 years ago a single box of 25 shells used for shooting skeet was a little more than $3.00, today that same brand of Winchester AA 12 ga. 8 shot is almost $10 and with the tax it would be $14.00)
• Banning semi-automatic shotguns like those used in hunting, skeet or sporting clays
• Serialization of ammunition and the requirement of individuals to destroy or expend any non serialized ammo by 2012 making the owning of non serialized ammunition a felony.
  
• Banning the personal reloading of ammunition (this combined with the proposed tax would effectively kill shooting sports. A competition shooter can easily shot 200 to 400 rounds of ammo per competition and 50 to 100 rounds per week in practicing. Reloads can cost as little as $3.50 per box of 25 compared to $14.00 with the tax; 200 rounds of reloaded ammo now can cost as little as $28 but with the proposed laws it would cost as much $112 putting the price of shooting competitively out of reach for normal citizens)
• Banning the use of lead in ammunition (this proposal goes to the floor in Washington state on January 26th) (This would also drive the cost of reloading through the roof!)
  
• Installation of a firing pin microstamp that ties ammunition to a certain gun (this is already performed in crime scenes with the use of rifling marks on recovered bullets; this is only requested to drive up the cost of owning a weapon)
• Registration of all firearms to include shotguns and hunting rifles, this also requires individuals to register with the FBI any firearm that is willed or given to them by family members this is currently illegal under federal law
  
• Creation of a national database that will include a photo, fingerprint, address and phone number of anyone owning a firearm. Same as above this is illegal under federal law.
• Make it a felony offense not to report a stolen, misplaced or lost firearm within 72 hours.
  
• Permanent reinstatement of the Brady Bill against weapons considered to be an assault weapon, take it from a former soldier; any weapon, including a common kitchen knife can be considered an assault weapon if someone wants to kill you.
  
• Making the owning of a weapon with a multiple ammunition feeder (i.e. magazines) a felony offense (almost all pistols fall into this category)
• Repealing the newly created law that allows a state's Right to Carry permit for individuals valid in National Parks
• Requirement to make weapons "Child Proof", by appealing to people's sympathy for children, they are attempting to make it almost impossible to make a gun. Can we do the same for cars or alcohol?
• Enacting laws that provide mandatory felony sentences to owners of guns who have their weapons stolen and used in a crime; specifically parents. Does this mean that a parent whose child willingly disobeys their parent and takes the parent's vehicle out and injures someone will be held to those same standards? If we can do this, can we also enforce those same sentences on parents when their children act violently toward teachers or join violent gangs and intentionally harm others during illegal acts?
• Limiting Right to Carry permits only to individuals who could prove that they are in risk of violent abuse or death.

UK Attempts Ban on Hunting

The UK is starting to see a surge in citizens protesting for the right to protect themselves and retain the right to legally hunt.

See this video entitled "The British called - They want their guns back!"  documenting the historical protest. This is something that Americans need to do (stage demonstrations for retaining our rights) now that we have an administration in Washington that wants to bend the 2nd Ammendment to their will.

Britain Unarmed and Unsafe

Britain has not only taken away individuals to own pistols but they have also passed laws that force imprisonment for defending ones self on your own property by use of a firearm; even if faced with a criminal intending death or dismemberment to you or your family.

One example of how they have used this law is to prosecuting an elderly man to life in prison after he shot 2 burglars (killing 1 and wounding the 2nd) who broke into his home in the middle of the night brandishing knives and willing to kill him. These were life criminals with over 50 arrests (some for violent crimes) between the two of them. Not only did they imprison the elderly man for defending his wife, but they also supplied the wounded man with a state sponsored lawyer that submitted a law suit against the elderly man's estate for "Pain and Suffering".

The criminals have taken note of the unarmed society and violent crime has since raised over 140%. With the violence already in place in the United States, a similar act in the US could make this country no safer than it is to live in South Africa. we can not stop drug trafficing today, if a gun ban was in place, those same routes used for drugs also allow for illegal trafficking of weapons. So violent gangs would still have access to the same weapons that they have now. The difference being is the law abiding citizens could not defend themselves legally and the criminals in this country would have a field day. With a possible depression on the horizon, crime will rise and it will be even more important for us as US Citizens to be able to defend ourselves for own safety.

Former UK Police Officer comments about 2nd Ammendment challenges

This was an interesting comment pertaining to the "Unarmed and Unsafe" article written by a Connecticut newspaper regarding Britain's rising violent crime rate since disarming citizens of their pistols.

" I find myself in total agreement with this article.As a former UK Police Officer,a member of the NRA and now a US resident,i saw at first hand the gradual suppression of gun ownership that led to a total handgun ban in the UK .This was compounded by the liberal lawmakers Blair and co who made a criminal of anyone who used a weapon for self defence.The result was an explosion in armed crime ,that led to even more panic laws such as a ban on replica and deactivated weapons.The crime rate continued to climb.The US agenda of the Brady campaign and the democratic party is all to familiar to me .Lets hope that The gun owners of the US are not so easily duped.If they are then the British Nightmare is also the US Future."
Steve Challis
Lexington Ky