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What Are Advanced Format Hard Drives?

A recent change to hard drive design may cause problems for older operating systems and for dual or multi-booting.

advanced format logo

Advanced Format hard drives became available at the start of 2010 and the first new PCs began to ship with them in early 2011, but it was mid 2012 before they started to become prevalent. Recent operating systems that are Advanced Format aware will configure the drives correctly for optimum use, but older operating systems and many current software tools for partitioning, cloning and imaging are unlikely to get it right.

Know Your Format.

Anyone installing or deploying an operating system or using an app that manipulates partitions would be advised to know the format of their hard drive and the capabilities of the OS and tools being used. The incorrect configuring of Advanced Format drives and partitions can lead to a performance loss. The use of an incompatible partitioning tool may result in the loss of partitions and data. Before you move on to our guide on the safe and optimum use of anything Advanced Format we hope this article might help to give you some insight into what it is all about. The main area of concern is one of partition alignment and we will try to explain with the use of a simple analogy what this is and why it matters. If you want to go on and delve into the real technical details you will find links at the bottom of this page.

What’s new about Advanced Format?

hard drive sector
The simple answer to that question is - larger sectors. The last couple of decades have seen a huge increase in hard drive capacity and the quantity of data that routinely gets moved around. Traditional hard drives have been tweaked again and again to keep up with the onslaught, but a bottleneck has been reached with the original design and so a more fundamental change is now required. The tiny regions known as sectors on the recording surface of a drive have been expanded to hold more data, so that fewer sectors have to be indexed and accessed during data transfers. The overheads involved in keeping track of and error checking vast numbers of individual sectors takes time and also uses up a surprising amount of disk space, so larger sectors will open the way for both a performance and capacity increase in the next generation of mechanical hard drives.

Like the Pages in a Book.
The way larger sectors have influence partition alignment has to do with how data is stored on, and then retrieved from, a hard drive. When data is written to a drive it will be split up into blocks so that each can be placed on a section of the drive that can be numbered and referenced so that the data can be found again. It is a bit like text being written to pages in a book, each page holds a fixed amount of text and that text can be found again by looking in an index for the page number. If we know how much text a page will hold we can split our data up into blocks to match the page size, which insures the best use of paper but it also means that when we come to retrieve a block of text we only need to locate and read one page. pages of a book

For everything to work as efficiently as intended we have to make sure that we start writing our block of data at the very top of a page so that the fixed amount of text in our block does not spill over onto a second page. If that were to happen we would have to look at two pages to read our single block of data. Pages in paper books are of course consecutive, but in computers this is not always the case so each page has to be individually indexed and referenced. Reading our single block of data from two pages is therefore going to take extra time, which if all our blocks of data spanned two pages could add up to a noticeable drop in hard drive performance, perhaps by 30% or more. So we have to align our blocks with our pages and to do this we simply have to make sure the very first page is aligned, so that all following pages are also naturally aligned. Get the first page wrong and all the following pages will be wrong.

We align things correctly by making sure that the partitions on the hard drive are created to begin at the top of one of the pages in our book. The default starting point of a traditionally created partition will not naturally line up with the start of the new larger Advanced Format page and will begin at a point inside the page where one of the smaller pages used to begin. To get our alignments correct we must therefore ensure that any app or tool we use that manipulates partitions will automatically work to the larger sector specifications, (or allow us to manually select partition settings). Old spec apps and tools should be avoided and any pre-Advanced Format operating systems we install such as WinXP should not be allowed to create their own out-of-line partitions. Conversely we need to take care when using a new spec tool or installing new operating systems on traditional hard drives. Using the new partition alignments on the old format drives should not in itself cause any issues and can in some cases be a good thing, but trying to mix partitions of both old and new alignments on the same hard drive may cause us some grief.

Vanishing Partitions.
Using the wrong alignments or mixing alignments on a drive can cause a performance hit and may even result in some system instability. The biggest concern and issues however come during the manipulation of partitions with an app or tool that automatically works to the opposite format of any partitions that are already present on Disk Destructora drive. In certain circumstances one or more existing partitions may get deleted or corrupted, with of course the loss of the data they contain. A big offender is Windows' own Disk Management utility, with both the XP and Vista/7 versions of the tool being capable of deleting an opposite format partition. Some older third party tools can also have a major problem with AF aligned partitions, most notably of which is the now out-of-date and unsupported Partition Magic and Drive Image. Both will want to repair what they see as errors in Advanced Format aligned partitions, which can render them inaccessible and unbootable. info iconNo More Magic. info iconAdvanced Format and Vanishing Partitions.

4k sectors logoAdvanced Format Sectors are 8 Times Larger.
The common traditional PC hard drive has sectors that are each 512bytes in size. The first generation of the new Advanced Format hard drives have sectors that are 4096bytes in size, which will span 8 of the old sectors. In computer terms 4096 bytes translates to 4 kilobytes, or 4K, and this is why you may see Advanced Format hard drives referred to as 4K drives. You may also see them referred to as 512e hard drives, where the e stands for emulation.

advanced format logoBehind the Scenes Emulation.
Current mainstream operating systems and software are so ingrained in working with 512byte sectors they are unable to work directly with the larger 4k sectors. This means that a translation from one to the other has to be carried out by the firmware in the hard drive’s inbuilt controller, which results in the outside world being unaware of the 4k sectors within. The Advanced Format drive pretends to be a traditional hard drive by emulating 512byte sectors, hence the reason why AF hard drives are also sometimes referred to as 512e drives.

What’s in a Name.
For the sake of keeping it simple we have so far made little distinction between Advanced Format drives and 4K sectors, so you can be excused if you thought they were one and the same. It is the emulation layer that sits between the operating system and the 4K sectors that is the component that gives Advanced Format drives their name. In the near future when operating systems and software can work directly with the new larger 4k sectors the emulation will be dropped and the drives will then simply be known as native 4K drives. As yet (Oct 2012) we have not seen any 4K native hard drives and it is likely that the first of them to come through will actually be Advanced Format drives that have a means of turning off the emulation, so converting them to 4K native.

(Update:-  The future has sneaked up on us again.....    Windows-8 and Server2012 support native 4K hard drives.)

Spanner guy  iconTech Bench - Extra real techie stuff for those who care or have to know.
If you examine our book analogy too closely it breaks down because of course we are not just dealing with individual pages (sectors), but clusters of sectors (aka File Allocation Units). The current Windows default for PC operating systems is 8 sectors per cluster, but it can be substantially more in the IT world of servers and RAID systems. It is 8 sectorsthe mis-aligning of clusters that is the cause of the performance hit from an incorrectly aligned partition. The legacy standards inherited from CHS disk controllers will start the first partition on an odd number of sectors, which can’t line up with the always even numbered cluster. info iconDisk Partition Alignment Best Practices for Servers/ Windows.
info icon Using Hyper-V with large sector drives on Windows Server 2008 / R2





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spacermultibooters.com: July 2012 - - Last reviewed or updated: Mar 2013


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