Changing the cache block size
You may be able to optimize performance for your workload by changing the block size of the cache.
Before you begin 
The default block size of 8 KB has been selected as optimal for most workloads. Check with your IBM representative to determine whether your configuration would benefit by changing the cache block size.
About this task 
This functionality is not available in FAMC. Use the Format-FACache Flash Accel PowerShell cmdlet to change the cache block size.
Information in the cache is erased for all disks on the virtual machine when you change the cache block size. The cache will take some time to be rewarmed after the block size is changed.
Steps 
1.
At a Windows command prompt, enter:
powershell
2.
Import-Module FA-PsCmdlets
3.
Enter the following command to disable the cache:
Set-FACache -AdminState Disabled
4.
Format-FACache -BlockSize <size> -BlocksPerChunk <number>
where size is the block size in bytes and number is the number of chunks per block. The default block size is 8 KB. The default number of blocks per chunk is 64. The chunk size (BlockSize × BlocksPerChunk) must be less than or equal to 1 MB. Ideally, the chunk size should be equal to the erase block size of the flash device.
5.
Set-FACache -AdminState Enabled
Result 
The block size is changed and caching resumes.
Parent Topic: Setting the cache size for virtual machines