I now this topic has been somewhat discussed before but I haven't managed to get a clear picture.
I’m trying to figure out whether partition alignment to erase block size is necessary with recent-ish SSD’s.
I have an OCZ Vertex 3 SSD with Windows 7 and Linux (XBMCbuntu) operating systems already installed in dual boot.

Gathered my drive’s block sizes from this thread on OCZTechnologyForum

  • Page size: 8 KB
  • File alloc. unit: 4 KB (ntfs)
  • Erase block size: 2048 KB

Windows 7 setup created the first partition with a 1MB offset (1048576 bytes).

Partition Disk #0, Partition #0     
Partition Size  48,83 GB (52.428.800.000 bytes) 
Partition Starting Offset 1.048.576 bytes 
Partition Disk #0, Partition #1     
Partition Size  31,23 GB (33.531.363.328 bytes) 
Partition Starting Offset 52.429.848.576 bytes 

The online tool SSD Aligment Calculator says the partition is misaligned regarding the erase block size since the latter is 2MB.

Since that online tool is oldish... is this correct ?
If so, is it important and worth the effort of moving around/resizing partitions to align to a 2MB offset and multiples-of boundaries?

  • Ejem... RFA, i.e., the thread at OCZ forum on first referenced link. Specifically posts #2 and #4. What are your sources?
    – danirod
    Oct 24, 2012 at 12:43
  • You may want to read this (old) article by Ted Tso (especially the last part). I would say: modern SSD may not need it, but if you can still do it easily, then it can only help.
    – Totor
    Oct 12, 2016 at 17:54

2 Answers 2


From OCZ's "The ABC Guide" to SSD's regarding alignment:

Default Vista and Win 7 create aligned partitions at an offset of 1024KiB.


Mac OSX Disk Utility aligns partitions in HFS+. As do most newer distros of GNU/Linux.

However, as you mentioned, the Vertex 3 has an erase block size of 2MB, which is not a factor of the current alignment offset; for this reason, I would indeed recommend moving the alignment to 2MB. From the OCZ forums, here's a guide on how to use gparted to align a SSD. There is also this tool for Linux to manually align a solid state drive.

  • Hmm, I may be confused here but taking into account the 2MB erase block size, shouldn't the first partition start at 2097152 bytes and the rest of boundaries aligned to multiples of that figure (2MB)? Just trying to work out if it's worth the hassle.
    – danirod
    Oct 24, 2012 at 12:47
  • @b4nd0ler0 sorry about the confusion, it appears you're right about the erase block size. I had read some conflicting figures from other people, but indeed the 2MB figure was revealed by an OCZ employee. Oct 24, 2012 at 12:52

Your data is stored on a SSD with a level of indirection at the block level. Each block can end up pretty much anywhere physically. Besides wear leveling some controllers compress blocks and point blocks with the same content to the same physical storage location.

The erase block size matters more in the effects it has on wear leveling, how much data might need to be copied elsewhere to free all blocks with content in the erase block before it's wiped (otherwise the SSD might eventually end up with only 1 block used per erase block) can also impact performance.

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