Align disk partitions on their cylinders, is, knowing that most frequent datas feet on a cylinder:

* Avoid to read 2 cylinders instead of one => gain time at read, reduce useless cache usage, gain bandewidth.
* Avoid to write 2 cylinders when only one is good enough => gain time, reduce useless cache usage, gain bandwith, reduce wearout
* For the previous reason, allow to grow greatly timelife of an SSD disk (number of writing cycles is limited on an SLC, more on an MLC, even more on a TLC, but the price of this last one is the lower by GB).

A simple method to know if your partitions are well aligned on cylinders

Launch cfdisk on the disk you want to optimize (replace /dev/sda, by the disk to optimize: /dev/sdb, /dev/sdc…):

cfdisk /dev/sda

If you see an asterisk (or star) at the most right of a partition ligne, this one is not aligned on cylinder. In my case, I have to remake all the partitions but sda3:

                           cfdisk (util-linux 2.20.1)

                              Disk Drive: /dev/sda
                       Size: 240057409536 bytes, 240.0 GB
             Heads: 255   Sectors per Track: 63   Cylinders: 29185

    Name        Flags      Part Type  FS Type          [Label]        Size (MB)
 ------------------------------------------------------------------------------
                            Pri/Log   Free Space                           1.05*
    sda1        Boot        Primary   ext4                             51158.98*
                            Pri/Log   Free Space                           1.22*
    sda2        Boot        Primary   ext4                             53686.01*
                            Pri/Log   Free Space                           0.41*
    sda3                    Primary   ext4                            135207.16
                            Pri/Log   Free Space                           2.62*





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                      Create new partition from free space

How to create an unique partition, using the whole disk and well fited

Using the old usagemode of fdisk. I found this tip on an Ubuntu documentation.

Replace /dev/sdX by the disk on which you want to create aligned partition:

fdisk /dev/sdX
c
u
p
n
[return key]
[return key]
[return key]
[return key]
w

Et voilà, you will see a beautifull result on cfdisk

To create several aligned partitions: Choose the good option instead of the 4 time [return key] and redo the n (new), for each partition.