Hello Experts,

We are trying to understand some of the performance benchmarch results that we have received from SQLIO test on windows 2012.

test scenerio: A windows VM residing on FC pool and it has three drives (C,E,F) all in the same datastore.        

C & E drives have same Allocation unit size (4K), C is MBR and E is GPT but as per SQL IO test, the throughput differs. C is slighly slower than E? Can we explain?

F drive has 64K allocation unit and gives best results which is expected.                                                                                                                                                                                                                                                                                                                                                                                            

	Operating System	Windows 2012 R2
	Storage profile	Silver
	File size for SQLIO	9 GB
	Disk layout:
	Drive letter	StartingOffset	Allocation unit size	Partition type
	C:	1024 KB	4096 bytes (default)	MBR
	E:	33 MB	4096 bytes (default)	GPT
	F:	33 MB	64 kilobytes	GPT
	Benchmark results:
	C:	IOPS	Throughput (MB/sec)		E:	IOPS	Throughput (MB/sec)		F:	IOPS	Throughput (MB/sec)
	Write - 8k random	20161	158		Write - 8k random	23905	187		Write - 8k random	25604	200
	Read - 8k random	25501	199		Read - 8k random	27253	213		Read - 8k random	27293	213
	Write - 64k sequential	8939	559		Write - 64k sequential	11905	744		Write - 64k sequential	14077	880
	Read - 64k sequential	17317	1082		Read - 64k sequential	21320	1333		Read - 64k sequential	21731	13

regards,

Saurabh