dcsimg

3TB Drives are Here

In real estate it's about location. In storage it's about capacity. The next crop of high density drives are available but there are some gotchas related to some 3TB drives that you need to know before making a land grab.

Act 1 – Scene 1

I see myself in a dark quiet room constructed of hastily thrown together cinder blocks painted some awful battleship gray, sitting on a cheap, squeaky, gray folding chair along with other balding middle-aged men. Cob-webs hang in the corners of the room and there is the faint smell of must and dust in the air. A confident and seemingly kindly, bearded gentlemen, well dressed but not over-dressed, steps to the front of the room in the light and welcomes all of us and thanks us for coming using his best calming voice. As with most everyone in the room the initial voice in my head says, “he doesn’t have a clue and I’m wasting my time.” Then quietly he asks that we introduce ourselves using the mantra that we have been taught over repeated meetings. I quietly sink into my chair and pray that I won’t be noticed and can quietly sit there during the meeting. However, my luck has run out like the squealing hard drive that is going bad in my storage array. The kind gentlemen looks in my direction and asks me, the person who has been a member of the group the longest, to start the introductions.

My knees shake slightly as I struggle to raise myself from the squeaky folding chair. I hope what little hair I have left is straight and neat despite the lack of attention I have given it over the last 48 hours while I was working on my squealing storage array in the data center. I stand and glance around the room quickly to see who is there before staring straight down at my shoes. I clear my throat. I clear it again. Then in a voice that is horse and cracking due to the overly dry air in the data center, I speak.

“Hello. My name is Jeff and I’m a storage capacity junky.”

I wake up in a sweat realizing it was just a dream. I didn’t have to explain myself, to admit to my peers in a badly written AA-esque meeting for storage administrators, that I want my storage capacity as large as possible. Instead I sit up, smile, and realize that all is right with the world because 3TB drives are easily available. It’s a good day after all.

However, as with everything, there are downsides to buying the latest and greatest 3TB drives and cramming them in my shiny Linux desktop and instantly growing my collection of K.C and the Sunshine Band mp3 (or ogg) clips.

In this article I want to talk about the new 3TB drive that Western Digital released in the last few months and things that you need to pay attention to while determining if the drive will work for your situation.

3TB Drives are Here!

If you follow the storage industry fairly closely it is no surprise that 3TB drives are here. On the other hand, if you don’t follow storage hardware developments that closely you might be surprised by 3TB drives being available. But then again, you might also expect storage capacity to keep growing, so their availability may not surprise you. Regardless, the 3TB drives are the largest capacity drives available in the market (at least right now).

The first company to release a 3TB drive was Western Digital that on Oct. 19, 2010, announced that they were actually shipping 3TB SATA hard drives. The Western Digital Green 3TB (Model: WD30EZRSDTL) is a very nice 3.5″ SATA hard drive. It uses five 600MB platters to achieve 3TB and has a SATA 2.0 (3 Gbps) interface with a very large 64MB cache. To keep the drive power down to a level that Western Digital wanted to achieve, this new drive has somewhere between a 5,400 and 6,000 rpm rotational speed. So it’s not a performance oriented drive but a capacity oriented drive.

As of the writing of this article, I checked www.newegg.com for pricing on the drive. The price on the drive was $209.99 (be sure to check pricing since this price was only when I checked and only at www.newegg.com). The drive also comes with a HighPoint RocketRAID 620 PCIe SATA card which is a bit unusual for SATA hard drives. Why would a standard SATA hard drive come with a SATA card when systems typically have lots of SATA ports? The answer is that is it used in breaking the 2.199TB limit for some systems.

What 2.199TB limit?

I suppose a number of readers are asking about this magic 2.199TB limit and why we are only seeing this limit now. So let’s start by reviewing why we have this limit.

Virtually every storage device used in the consumer world as well as most in the enterprise world use a scheme called LBA to address the blocks on storage devices. The approach is really simple – it is a linear addressing scheme where blocks are located by an integer index. The first block is LBA 0, the second is LBA 1, and on and on. When you system boots, it looks at LBA 0 of the first boot device for the Master Boot Record (MBR).

The LBA scheme uses 32-bit addressing under the MBR partitions. This means that the maximum possible LBA value is,

Maximum LBA Value = 2^32 = 4,294,967,296


Since most drives use 512-byte sectors this means the largest partition is limited to the following size.

Largest Partition = 4,294,967,296 * 512 bytes = 2,199,023,255,552 Bytes


In other words, we can’t address more than 2.199 TB’s on a single drive with a MBR partition.

There are many ways to solve this problem. One way is to support a larger LBA address space. In particular, 64-bit LBA addressing will allow us to go to 2^64 blocks. Coupling this with 512 byte sectors this gets us to about 9.4ZB (Zettabytes). You will be very pleased to note that Linux has 64-bit LBA addressing, particularly for SATA. From what I understand, 64-bit LBA has been in there for SCSI drives so it was easily adapted for SATA drives.

Another approach to solving the problem is to increase the size of the sectors from 512-bytes to something bigger, such as 4KB. Let’s take a quick look at this.

4KB Sectors

As we previously saw, using really small sectors, such as 512-byte, can limit the amount of addressable space using 32-bit LBA addressing. The 512 byte sector size was originally used to get the maximum usable capacity from storage. Such a small sector size almost guaranteed that sectors would not go wasted since it was extremely unlikely that a file would be smaller than 512 bytes (it’s possible but very unlikely). But now we are facing the problem that we can’t use hard drives larger than 2.199TB which has become an obstacle for us storage capacity junkies. One apparently easy option is to increase the sector size to 4KB.

Why 4KB? The answer is surprisingly simple – it matches an integer multiple of various system aspects. Specifically, the NTFS and HFS+ file systems all default to 4KB clusters. Ext3 also defaults to 4KB. Just as important is the fact that the normal page size of memory on an x86 processor is 4KB. So memory and several common file systems all are based on 4KB (By the way – that’s not coincidence. It’s all based on the x86 memory page size). Using 4KB means that we are wasting as little space as possible since we’ve matched the memory page size and the file system cluster size. However, there will be times when the file is smaller than 4KB so it will effectively waste space. But this is the trade that must be made in exchange for getting much large capacities. So 4KB it is.

It turns out that 4KB sectors also have other benefits that impact the drives themselves. As the aural density (the density of data on the platter) increases, the ability to access the data becomes more difficult. You either need much more sensitive drive heads (adding cost and complexity) or you need to improve your ability to read the data correctly. Drives use ECC (Error Checking Correcting) algorithms inside the drive itself to make sure they are reading the sectors correctly. In current 512 byte sector drives, when the data is written, a 4 byte (40 bits) block of ECC data is also written. When the particular 512 byte sector is read, the ECC data is read as well. The drive then compares the values. If they are not equal (ouch) then the drive re-reads the data and repeats the process until the data matches or until it reaches a particular value (a time-out) and will throw an ECC error. The drive can use CRC codes and Reed-Solomon codes to recover data from sectors that have bad (corrupt) data and to move that data to spare sectors. This is what you commonly see in SATA drives when a sector goes bad and the drive remaps the data from that sector to a new spare sector on the drive.

Using the 512 byte sectors, we need 8 sectors to reach a total of 4KB of data. This means we have 8*40 = 320 bits (or 32 bytes assuming 10 bits = 1 byte) of ECC data to reach 4KB of real data. On the other hand, if we have 4KB sectors, Western Digital is saying we only need 100 bits (10 bytes) of ECC data. This means we can save about 220 bits (22 bytes) in space that can be used by the user (and us storage capacity junkies rejoice). This give about 5.5% more capacity per drive.

In addition to capacity, the switch to 4KB sectors also means that the drive does not have to do as much work per read when performing the ECC check, improving drive performance. Also, it means that the 4KB drive can correct sectors faster than the 512 byte sector drives. Both aspects help performance.

Next: Other Operating Systems

Comments on "3TB Drives are Here"

It’s not that I want to duplicate your internet site, but I really like the style. Could you let me know which style are you using? Or was it tailor made?

What are you stating, man? I realize everyones got their own thoughts and opinions, but really? Listen, your website is awesome. I like the hard work you put into it, especially with the vids and the pics. But, come on. Theres gotta be a better way to say this, a way that doesnt make it seem like most people here is stupid!

I loved your blog post.Much thanks again. Really Great.

I simply want to say I am very new to blogging and site-building and actually savored your web blog. Likely I’m likely to bookmark your blog . You absolutely come with great well written articles. Thanks a lot for sharing with us your blog site.

Feel frеe to suгf tօ mу ᴡᥱƅ
ѕіtе – Top of page

Here is my weblοg :: ????????

Superb read, I just passed this onto a colleague who was doing a little research on that. And he actually bought me lunch because I located it for him smile So let me rephrase that: Thanks for lunch!

You…are…my…hero!!! I cant believe something like this exists on the internet! Its so true, so honest, and more than that you dont sound like an idiot! Finally, someone who knows how to talk about a subject without sounding like a kid who didnt get that bike he wanted for Christmas.

Hi, I just found your web site via google. Your viewpoint is truly applicable to my life right now, and I’m really delighted I discovered your website.

Superb read, I just passed this onto a colleague who was doing a little research on that. And he really bought me lunch because I located it for him smile So let me rephrase that: Thanks for lunch!

Have you thought about adding some social bookmarking buttons to these blogs. At least for twitter.

What you said made a lot of sense. But, think about this, what if you added a little content? I mean, I dont want to tell you how to run your blog, but what if you added something to maybe get peoples attention? Just like a video or a picture or two to get people excited about what youve got to say. In my opinion, it would make your blog come to life a little bit.

Thank ʏou for any orһer іnfⲟrmɑtіᴠᥱ Ƅⅼοǥ.
Ꭲhᥱ рlɑcᥱ
еlsе may јuѕt
Ι ǥet tҺаt ҝіnd оf іnfօ ѡrіttеn іn ѕucɦ а pегfеct
ѡаy? Ⅰ’ᴠe ɑ ргߋjеct tҺat Ⅰ’m simρlү noա
гսnnіng оn, and I ɦavе bееn аt tɦе lⲟоқ ⲟսtt foг
ѕuch іnfо.

Ӎү ᴡebѕіte Alberto

What you said made a lot of sense. But, think about this, what if you added a little content? I mean, I dont want to tell you how to run your blog, but what if you added something to maybe get peoples attention? Just like a video or a picture or two to get people excited about what youve got to say. In my opinion, it would make your blog come to life a little bit.

Many thanks for sharing this first-class piece. Very inspiring! (as always, btw)

I have read a few of the articles on your website now, and I really like your style of blogging. I added it to my favorites blog site list and will be checking back soon. Please check out my site as well and let me know what you think.

Excellent read, I just passed this onto a colleague who was doing a little analysis on that. And he actually bought me lunch because I found it for him smile So let me rephrase that: Thanks for lunch!

Awseome article, I am a big believer in placing comments on blogs and forums to inform the blog writers know that they’ve added some thing useful to the world wide web!

Youre so awesome, man! I cant believe I missed this blog for so long. Its just great stuff all round. Your design, man…too amazing! I cant wait to read what youve got next. I love everything that youre saying and want more, more, MORE! Keep this up, man! Its just too good.

You lost me, friend. I mean, I imagine I get what youre declaring. I have an understanding of what you are saying, but you just appear to have forgotten about that you’ll find some other individuals within the world who look at this issue for what it truly is and may not agree with you. You may well be turning away alot of persons who may have been supporters of your website.

Ha ha… I was just browsing around and took a glimpse at these reviews. I can’t believe that there’s still this much attention. Thanks for writing about this.

Have you considered about incorporating some social bookmarking buttons to these blogs. At least for google.

Good Post, I am a big believer in commenting on websites to inform the blog writers know that they’ve added some thing of great benefit to the world wide web!

Thanks for sharing this very good article. Very interesting ideas! (as always, btw)

Congratulations for posting such a useful blog. Your blog isn’t only informative but also extremely artistic too. There usually are extremely couple of individuals who can write not so easy articles that creatively. Keep up the good writing !!

Im no expert, but I think you just crafted an excellent point. You definitely comprehend what youre speaking about, and I can definitely get behind that. Thanks for staying so upfront and so straightforward.

What are you indicating, man? I recognize everyones got their own view, but really? Listen, your web site is awesome. I like the work you put into it, specially with the vids and the pics. But, come on. Theres gotta be a better way to say this, a way that doesnt make it seem like everyone here is stupid!

Have you thought about introducing some social bookmarking buttons to these blog posts. At least for twitter.

Ha ha… I was just browsing around and took a glimpse at these reviews. I can’t believe that there’s still this much interest. Thanks for posting about this.

Congratulations on having one of the most sophisticated blogs Ive come across in some time! Its just incredible how much you can take away from something simply because of how visually beautiful it is. Youve put together a great blog space –great graphics, videos, layout. This is definitely a must-see blog!

I have read a few of the articles on your website now, and I really like your style of blogging. I added it to my favorites blog site list and will be checking back soon. Please check out my site as well and let me know what you think.

Have you considered about putting some social bookmarking buttons to these blogs. At least for twitter.

Hey there this is a fantastic article. I’m going to email this to my associates. I came on this while searching on yahoo I’ll be sure to come back. thanks for sharing.

Hi, I just ran across your weblog via Bing. Your viewpoint is truly pertinent to my life at this moment, and I’m really pleased I found your website.

Heya this is a fantastic article. I’m going to mail this to my friends. I came on this while exploring on aol I’ll be sure to come back. thanks for sharing.

I was very glad to find this site on yahoo.I wished to say thank you to you with regard to this superb article!! I surelyloved every little bit of it and I’ve you bookmarked to have a look at new stuff you post.

pretty helpful material, overall I feel this is really worth a bookmark, thanks

Ha ha… I was just surfing around and took a look at these comments. I can’t believe that there’s still this much interest. Thanks for crafting articles about this.

What you said made a lot of sense. But, think about this, what if you added a little content? I mean, I dont want to tell you how to run your blog, but what if you added something to maybe get peoples attention? Just like a video or a picture or two to get people excited about what youve got to say. In my opinion, it would make your blog come to life a little bit.

I have read a few of the articles on your website now, and I really like your style of blogging. I added it to my favorites blog site list and will be checking back soon. Please check out my site as well and let me know what you think.

Congratulations on having one of the most sophisticated blogs Ive come across in some time! Its just incredible how much you can take away from something simply because of how visually beautiful it is. Youve put together a great blog space –great graphics, videos, layout. This is definitely a must-see blog!

Your current blogs always have many of really up to date info. Where do you come up with this? Just saying you are very inspiring. Thanks again

You…are…my…hero!!! I cant believe something like this exists on the internet! Its so true, so honest, and more than that you dont sound like an idiot! Finally, someone who knows how to talk about a subject without sounding like a kid who didnt get that bike he wanted for Christmas.

I was very ecstatic to find this site on bing.I wanted to say many thanks to you with regard to this fantastic article!! I undoubtedlyappreciated every little bit of it and I’ve you bookmarked to have a look at new stuff you post.

It’s not that I want to duplicate your web-site, but I really like the pattern. Could you let me know which style are you using? Or was it especially designed?

I hope you never stop! This is one of the best blogs Ive ever read. Youve got some mad skill here, man. I just hope that you dont lose your style because youre definitely one of the coolest bloggers out there. Please keep it up because the internet needs someone like you spreading the word.

Leave a Reply