Hey all, I plan to install a 128GB SSD later today in my mid-2010 MBP 13" to complement the existing 256GB HD. I will back 'em up and join them using this guide in order to roll my own Fusion drive.
My question is, does it make sense to under-provision the SSD (i.e. leave unpartitioned space)? Anandtech explains how having some un-provisioned space on the drive can enhance the performance and extend the life of an SSD. It seems like the Fusion algorithm will default to filling the SSD less 4GB, a write buffer that it will use up on an as-needed basis. Anandtech explains that most desktop uses of SSDs doesn't require more than the ~7% of automatically unallocated space in order to maintain good performance and drive life.
BUT... A Fusion drive with more data than the SSD can hold is not a typical desktop use of the SSD! You won't be leaving much partitioned space unused ever -- you will constantly be floating between (Capacity-4GB) and (Capacity) amounts of data on the SSD if you have enough data to spill over to the HDD. For this reason I'm thinking of allocating only 90% of the SSD when I roll the Fusion drive, to leave the controller with more unallocated headroom to work with for wear-leveling, fast writes, less write amplification, etc.
Does this strategy make sense to those of you who think about the engineering of SSDs? Is the Fusion drive a good example of a "not-a-normal-desktop-use" from the SSD's perspective? I am concerned that the automatic tiering done by the OS will prematurely wear down the SSD and/or affect the SSD's performance otherwise.
My question is, does it make sense to under-provision the SSD (i.e. leave unpartitioned space)? Anandtech explains how having some un-provisioned space on the drive can enhance the performance and extend the life of an SSD. It seems like the Fusion algorithm will default to filling the SSD less 4GB, a write buffer that it will use up on an as-needed basis. Anandtech explains that most desktop uses of SSDs doesn't require more than the ~7% of automatically unallocated space in order to maintain good performance and drive life.
BUT... A Fusion drive with more data than the SSD can hold is not a typical desktop use of the SSD! You won't be leaving much partitioned space unused ever -- you will constantly be floating between (Capacity-4GB) and (Capacity) amounts of data on the SSD if you have enough data to spill over to the HDD. For this reason I'm thinking of allocating only 90% of the SSD when I roll the Fusion drive, to leave the controller with more unallocated headroom to work with for wear-leveling, fast writes, less write amplification, etc.
Does this strategy make sense to those of you who think about the engineering of SSDs? Is the Fusion drive a good example of a "not-a-normal-desktop-use" from the SSD's perspective? I am concerned that the automatic tiering done by the OS will prematurely wear down the SSD and/or affect the SSD's performance otherwise.