Storage technologies are evolving. Hard drive capacities are steadily increasing into the Terabyte range, and industry standards are changing to ensure such large drives are both reliable and perform well.
Until recently, PC hard drives always had 512 bytes per sector for both physical and logical sectors. Because of this, existing Microsoft Windows operating systems and utilities were optimized for 512 byte sectors. Specifically, file system utilities, disk imaging tools, backup utilities, and other types of software were optimized to provide maximum performance using drives having 512 byte per sector.
Benefits of Advanced Format Drives
Now beginning to appear in the marketplace however is the first generation of PC hard drives having a larger sector size than 512 bytes. These drives are commonly called Advanced Format drives, and they have physical sectors of size 4096 bytes. This eight-fold increase in bit density has two main benefits:
- It allows for much higher hard drive capacity without requiring more platters in the hard drive.
- It improves error correction by allowing for use of longer ECC code words which can result in increased reliability for data transfers.
The problem however with increasing the number of bytes per physical sector like this is that key operating system components such as file system drivers and backup utilities have historically been optimized to work with 512 byte sectors. As a result, simply changing bytes per sector from 512 to 4096 may cause some of these components to fail to work properly or become unreliable in their operation. Advanced Format solves this problem through emulation—the hard drive interface "translates" each 4096 byte physical sector into eight 512 byte logical sectors. Because of this emulation, Advanced Format drivers are sometimes called 512e drives (the "e" stands for "emulation").
Support for Advanced Format Drives in Windows Operating Systems
Support for Advanced Format drives in Windows operating systems is an evolving thing. Here's the run-down:
Windows XP, Windows Server 2003 and Windows Server 2003 R2 – First, versions earlier than Windows Vista do not include any built-in support for Advanced Format drives, so if you simply insert a 512e drive into a box running Windows XP or Windows Server 2003 and try to use it, you can end up with problems related to the performance and reliability of these drives. Fortunately, makers of Advanced Format drives like Western Digital can provide software for these platforms that may address some of these issues. For example, Western Digital provides a utility called WD Align Windows that purportedly enables Advanced Format drives to operate at full performance on these earlier versions of Windows by aligning partitions properly. However, performance degradation has been observed when using Advanced Format drives on older Windows operating systems, so vendor-supplied utilities like these may have limited benefit for certain kinds of scenarios.
Windows Vista– Built-in support for Advanced Format drives on Windows operating systems was first introduced with Windows Vista. Specifically, Vista can sometimes identify when a hard disk is 512e type but that's about all and it can only do this certain bus types and drivers.
Windows Server 2008 – Same support as Windows Vista above.
Windows 7 – The RTM version of Windows 7 includes improved support for Advanced Format drives. However, there were some problems related to this support, so a hotfix was later released by Microsoft to address these issues. See KB 982018 for details. More information can be found on this blog post from the Storage Team at Microsoft.
Windows Server 2008 R2 – Same support as for Windows 7 RTM above with certain exceptions. For example:
- The Hyper-V server role is not compatible with Advanced Format drives. That's because the VHD driver assumes the physical sector size is 512 bytes and therefore use 512 bytes IOs. In other words, VHDs are 512k aligned, so if you store VHD files on a 512e drive then the Hyper-V won't be able to open the VHD files. For more details, see KB 2515143.
- Microsoft SQL Server is not fully compatible with Advanced Format drives. Specifically, if you store a SQL Server database or log file on a 512e drive, the result can be poor performance and even loss of data integrity. For more information, see this blog post from Microsoft Customer Service and Support (CSS).
Windows 7 SP1 and Windows Server 2008 R2 SP1 – The hotfix described in KB 982018 is included as part of Service Pack 1 so these operating systems now provide the best support for 512e drives of any Windows operating systems. For details, go to Windows Server 2008 R2 Service Pack 1 on TechNet and click Notable Changes in Service Pack 1 for Windows 7 and Windows Server 2008 R2, then download the Word file Notable Changes in Windows 7 and Windows Server 2008 R2 Service Pack 1.doc.
Identifying Advanced Format Drives
Other than by consulting vendor-supplied documentation, how can you determine whether a PC has any Advanced Format drives in them? Fortunately, Keith Garner of Xtreme Consulting Group has created a free utility called IsAdvancedFormat.exe that can do just that. See this blog post for details and to download the tool.
Why can't you use the System Information tool Msinfo32.exe to do this? Msinfo32 that is included in all versions of Windows from Windows XP onwards, and you can use it to gather information about a computer, diagnose issues, and access other troubleshooting tools. If you run this tool and select Components and then Disks, you can view the sector size of each hard drive on the system (see Figure 1). Unfortunately, Msinfo32 uses WMI to obtain this information, and this means it reports the logical sector size, not the physical sector size. As a result, your 512e drives will be reported as 512 bytes/sector by Msinfo32.
Figure 1: Msinfo32 reports 512 bytes/sector for both traditional hard drives and newer 512e drives.
If you have the latest version of the KB 982018 hotfix installed however, you can also use the fsutil fsinfo ntfsinfo <drive>:\ command to determine whether a drive on the system is 512e type.
Why Does All This Matter?
Reports are that OEMs like HP, Dell and Lenovo will begin shipping Advanced Format drives when their current inventory of standard 512 sector drives become depleted, and this may have already happened by the time you're reading this article. In other words, if you are still using Windows XP in your environment and you order new systems from your OEM, these systems may have Advanced Format drives in them. And even if the partitions of these drives have been aligned using vendor-supplied utilities, some degradation of performance may be the result compared to system having standard 512 sector drives.
What's the moral of the story? Accelerate your migration to Windows 7 SP1 and you'll not only benefit from the increased security and other improvements in this new operating system but you'll also be able to take full advantage of the improved reliability and greater capacity of Advanced Format drives.
For those interested, the following is some additional information on the subject of Advanced Format drives:
- Western Digital’s Advanced Format: The 4K Sector Transition Begins (AnandTech)
- Exploring WD's Advanced Format HD Technology (HotHardware)
- Information about Microsoft support policy for large sector drives in Windows (Microsoft Support)
- 512-byte Emulation (512e) Disk Compatibility Update (MSDN)