SQL Server reads and writes in 64K blocks.
Therefore , format drives you provision for SQL data & logs with a cluster size of 64K.
Simple Really :)
Partition Alignment
Before you format the drives however, there is the matter of Partition Alignment.
The following formulae are published by Microsoft to help determine partition alignment.
Partition_Offset / Stripe_Unit_Size = integer (this is the most important)
Stripe_Unit_Size / File_Allocation_Unit_Size = integer
In the absence of the stripe size info, the alignment should at the very least be changed from it’s 32K default when establishing the partition.
If we can’t find Stripe size information, the best we can do is use an alignment value of 1024K (1MB) which is common to many SANs and is compatible with the 64K Cluster size.
NB : Alignment is handled automatically on Windows 2008.
IT Knowledgebase : How much performance are you losing my not aligning your drives?
MSDN : Disk Partition Alignment Best Practices for SQL Server
To set alignment >
C:\>DISKPART
Microsoft DiskPart version 5.1.3565
Copyright (C) 1999-2003 Microsoft Corporation.
On computer: DEV008
DISKPART>SELECT DISK 1
Disk 1 is now the selected disk
DISKPART>CREATE PARTITION PRIMARY ALIGN=1024
DiskPart succeeded in creating the specified partition
You'll then want to format the drive in a 64K cluster size.
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