L2arc write amplification

[romanshein]

I've setup a basic read-only cache and noticed a puzzling fenomena:
Total writes: 185.9 Mb
Total reads: 1.5 Gb
L2Storage writes: 2.5 Gb
2.5-1.5-0.19=0.8 Gb of amplified writes.Why?
Both block and sector size are 64kb on ntfs volume on Win7x64sp1

[Support]

For better performance, PrimoCache may store whole block or adjacent blocks to l2 cache even currently system only reads a part of a block. So usually "L2 Write" will be larger than "Total Reads" + "Total Writes".