Windows 10: Partition created by Windows Disk Management not aligned with SSD physical block size of 4K...

I formatted a new disk using the windows disk management that comes with Windows 10. I chose GPT. Then i checked the result. As you can see in the output below the Start sector is 34. With a physical block size of 4K bytes, and logical size of 512 byte, the start sector needs to be a multiple of 8 for proper alignment to occur. 34 is not divisible by 8, remainder is 2, so the partition is not correctly aligned. The following Microsoft basic data partition is correctly aligned, which makes me believe that this is an oversight.Start End

:)

 

Partition Alignment Spreadsheet

I created an excel spreadsheet that auto-calculates whether your raid array is properly aligned. It also auto-calculates non-raid partitions. You must meet the requirements of all Rules to be considered Aligned.

Using this spreadsheet's calculations, TechPowerUp!'s W1zzard wrote a great Javascript applet that calculates SSD alignment without the need to download the spreadsheet! The Javascript applet is linked below.

You must input your own data. It will not fetch your system information automatically. That's why the example column is there.

Let me know of any corrections or additions I can make to the sheet.

Partition alignment is the single most important performance tweak you can do for any SSD.

Lets break it down to it's simplist form. The SSD is divided into Blocks of 512k which are divided into pages of 4k in most cases. 128 pages = 1 block.

There is a certain amount of space before the start of the first partition, which is what is referred to as the offset. Vista and W7 use a default offset of 1024k, meaning there's 1024k of empty space before the partition. Starting at 1024k means that the partition starts at the beginning of the third block, since blocks are 512k (512k x 2 = 1024k).

The goal is to not start a partition in the middle of a block or a page. That way, you don't split any boundaries. If you split a page (4k) section, then 2 writes are necessary to write the page instead of 1, doubling the work. It will happen repeatively every 8th page, reducing overall performance and I/O commands. Blocks have a similar performance hit but not to the same degree as pages. It's easy to align to both.

Alignment has to be done when the partition is created. There are tools such as a gparted boot CD that can change alignment after it's created, but it's not 100%. Sometimes, you can lose your data with that method. It's best to fresh install and correctly create the partition at the beginning. Windows Vista/7 will both correctly align a partition. You must not have any previous partitions on the SSD and allow Windows to create and quick format the partition during the installation procedure.

WinXP is another story because it will not align a partition correctly by default. Extra steps are involved. The easiest way to align a WinXP OS volume is to get the downloadable Vista Recovery DVD and create the OS partition before the installation of WinXP. The partition created by the Vista Recovery DVD will be the same as the Vista Installation DVD and will be aligned at 1024kb by default which is a valid alignment for todays hardware.

It takes a moment to wrap your head around the new technology, but the sooner you forget HDDs, sectors, tracks, and cylinders, the better off you'll be. It's all about the blocks and pages now.

Online SSD Alignment Calculator written by TechPowerUp!'s W1zzard.

VBScript Alignment Checking Tool originally written by TcpDump's Tom Hirt. Discovered by Halk and edited by me to work with all SSDs with 512kb block sizes.

SSD Alignment Spreadsheet created by me.

Jason

 

Partition Alignment Spreadsheet




SSD Drive Specifications:

All OCZ Drives to date
NAND Page = 4096 bytes (4k)
NAND Erase Block Size = 524288 bytes (512k)

Intel X25-M
NAND Page = 4096 bytes (4k)
NAND Erase Block Size = 524288 bytes (512k)

G.Skill Falcon
NAND Page = 4096 bytes (4k)
NAND Erase Block Size = 524288 bytes (512k)

Supertalent Ultra Drive GX
NAND Page = 4096 bytes (4k)
NAND Erase Block Size = 524288 bytes (512k)

Patriot Torqx
NAND Page = 4096 bytes (4k)
NAND Erase Block Size = 524288 bytes (512k)

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Consolidated list of threads containing info on parititon alignment:

http://www.ocztechnologyforum.com/forum/showthread.php?t=48309 by therookie
http://www.ocztechnologyforum.com/forum/showthread.php?t=55238 by Chrisped
http://blogs.msdn.com/jimmymay/archi...-template.aspx
http://www.ocztechnologyforum.com/forum/showthread.php?t=50376 by Tony

**Notice- These guides will recommend all sorts of partition offsets. SSDs are divided into pages and blocks. Early guides did not take in the importance of aligning to blocks, but instead only pages. Please use the recommended partition alignment of 1024kb (Vista and W7 default) or you may not be aligned to the blocks which can result in less IO performance.

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Commands to check alignment:

start > run > type "cmd" to enter command prompt, then type "wmic partition get Name,StartingOffset,Size". This method works in XP, Vista and W7.

or

within windows, type msinfo32. When the info program runs, navigate to Components > Storage > DISKS and look for "partition starting offset" with a value in bytes. This method works in XP, Vista and W7.

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Some alignment misconception:

I've seen some on the forum state that "sectors/track" is what to check when looking at alignment. That is incorrect.

In Tony's post HERE, he states that the start of the first partition begins on sector 63 in Windows XP which we all know as the default misaligned partition. Sector 63 is the same as 32256 byte offset. Sectors/Track is a totally different disk parameter and has NOTHING to do with disk alignment. Tony was not referring to Sectors/Track.

The math behind it is: starting offset / bytes per sector = starting sector boundary
In the case of windows xp: 32256 / 512 = 63rd sector (not sectors/track)
In Vista/W7: 1048576 / 512 = 2048

HERE is a good read on how disk technology has evolved and why "63 sectors/track" means nothing.

Jason

 

W7 Hard drive partition issue

to get rid of that 100 meg windows partition that setup creates for you on a new install on a blank hdd:

- press shift+f10 when on the partition management screen in setup <-- this opens a command prompt
- diskpart <-- start the windows command line partition management tool
- list disk <--- list the installed hdds in this computer for the next step
- select disk 0 <- might have to replace 0 with the number of the correct disk
- clean <-- this will erase all data on the disk you selected one step up- dont use the wrong disk!
- create partition primary <- creates a primary partition taking up all space on the drive, adjust the command if necessary
- exit, exit to exit diskpart and the command prompt
- click refresh in partition manager and select your newly created partition and install to that