On 2016-09-22 20:44, Mike Gossett wrote:
my sales guy basically said the guarantee works as follows - they don't hit the 4:1 target, they buy you whatever amount of shelf\ssd required to makeup shortfall.
*duh*
The magic has to do with what they call "compaction" - writes <4KB (down to 512B/ea) are "compacted" into a single 4K block... this apparently adds to the std dedupe and compression they use.
Well, magic or not... the answer *must* be: it depends. Note the expressions below "if", "can be" etc.
- - - Currently Data ONTAP writes data to storage media in 4KB blocks * An I/O or file has less than 4KB of data uses an entire 4KB
Adaptive compression can compress an 8KB I/O into a 4KB block on storage * If the I/O is >50% compressible it is stored in a 4KB block – maximum storage efficiency ratio is 2:1
Storage space savings can be increased considerably if multiple small I/Os or files can be stored together in a 4KB block
* Data ONTAP 9 does this with inline data compaction * Turned on by default on AFF; can be turned on manually for hybrid systems
/M