i've heard it said- why partition with ssds

i'm wondering why they would say that. Is the situation different from with spinning disk style hard drives.

The reasons with spinning disk drives, were

-smaller partitions are quicker to defragment

-could be quicker to format (though there is quickformat!)

-organization separating data and system onto separate partitions, and can wipe the system partition.

I know somebody may look at those reasons and still not partition a drive. But I am interested in what the reasons are, with partitioning an SSD drive, how the situation differs if at all?

Somebody suggested why not buy a few small SSDs. Though surely the same logic would apply to partitioning non-SSD drives? And surely with either, one is limited by the number of SATA ports.

And is the issue of partition alignment something that is relevant to both SSD and non-SSD? i've only heard of it recently, in SSD times.

  • Similar Question, not a duplicate really though: superuser.com/questions/86753/…
    – Urda
    Oct 14, 2010 at 15:15
  • I think the only relevant point in my question was the last one.. about partition alignment, hence that was what people responded to. The rest of it was largely based on what a silly guy said that prompted me to think ask the question.
    – barlop
    Oct 19, 2010 at 21:48

3 Answers 3


The reason for using a partitioning scheme would be to allow for the presence of a Master Boot Record. Since one is only needed on the first hard drive, subsequent hard drives can have only a single volume taking up the full disk.

Partition alignment isn't a big deal in platter drives since they're so slow regardless that it really won't make that much difference.

  • how much does the MBR take up and how do you know?
    – barlop
    Oct 14, 2010 at 16:18
  • At first I thought that there wasn't a big difference between partitioned and unpartitioned, but then I got thinking about things like LVM and the PV header. The MBR takes up the first 460 bytes of the first 512-byte sector on the drive, with the (MS-DOS) partition table taking up the rest. If the entire drive is being used as one volume then the first sector is being used for the filesystem or PV headers, rendering it unavailable for the MBR. Oct 15, 2010 at 0:49
  • But partition alignment is not required on Vista onwards, as it does it automatically.
    – paradroid
    Oct 19, 2010 at 23:12

We bought a ton of Intel SSD's, and it was suggested by some tech's at microsoft that we move to a single Partition (note, these guys are senior account techs, not storage system engineers, so YMMV). They said SSD's use free space on the partition to do its wear leveling. If you have a 160GB SSD, that is half full, then you have 80GB of free space to wear level with. However, if you have two 80GB partitions, and both are half full, then the each partion only has 40GB of space for wear leveling. If one partition gets written to more often, then having less space for wear leveling can wear out the drive faster.

Not to mention, its just in-efficient if you have one partition almost full, and another mostly empty, your artificially constrained.

Many people do partitions so when they re-install, they can format the drive that has their apps and OS, and then re-install, and leave their data on another drive. With USMT 4.0, and it hardlink migration, it is faster to have a single partion, and just re-install windows over the top.

  • 1
    They don't do wear leveling with free space in the partition, they do wear leveling with unpartitionable space on the drive. Oct 14, 2010 at 12:58
  • 1
    What Ignacio said - the capacity of these Intel SSDs is about 15-20% higher than advertised, the excess space being used for wear leveling. Also be aware - if you're following your own advice of "re-install[ing] windows over the top" that you should probably recreate the partition from scratch if that drive ever had Windows XP, OS 9, or any old flavors of Linux on it - those partitions are misaligned for the pages on the SSD and you'll get a serious write amplification effect. (Vista/7, most newish builds of Linux are smart enough to format these aligned correctly.)
    – Shinrai
    Oct 14, 2010 at 14:13

The only reason I can think of that partitioning makes easier is backups. Now that most partition types have some form of Block Sub-Allocation, the other main reason (smaller block sizes) to partition a drive has been diminished.

Alignment on a single drive might be negligible, across an array, it does help reduce reads.

As for the wear leveling, that will still be per device since it happens at a lower level on the media than partitions and logical volumes occur. When in hardware RAID, the full media space is considered for writes to be active so consistency checks are performed on all sectors not just the ones with data in them. This is why rebuild time is a function of slice size and not a function volume capacity.

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