Actually, VMFS IO size is not related to the VMFS volume block size. IO size from VMFS is the same as that issued by the Guest OS. The VMFS block size only relates to the minimum/maximum size of files in the VMFS and the VMFS itself.  Yes, 1MB is a large IO, in fact, by default CLARiiON bypasses write cache for IO’s 1MB or larger (this is configurable). There is actually little or no benefit from write cache when dealing with IO’s that large and generally the host and disk can outperform the cache so cache becomes a bottleneck.  As far as your other questions, if the IO size was 1MB, it would fill 4 stripes and would still be good sequential workload. For a 4+1 RG, the 1MB IO would write out about 1.2MB of data in total ((256KB stripe + 64KB parity) * 4) to the back end disks. The 1MB host IO would end up being 4 back end IO’s to disk but that’s not really an issue in this case. You could create an 81 RAID group which would give you a 512KB stripe in which case the 1MB IO would be 2 IOs. But in reality, 41 is a sweet spot for Clariion.  By comparison, a 1MB write to a RAID10 4+4 group would write out 2MB to the backend disks.  A 1MB write to a RAID6 4+2 group would write out about 1.4MB of data ((256KB + 128KB) * 4)  Richard J Anderson
What is the best RAID configuration for a VMWare VMFS datastore that will be holding backups for various SQL: servers. We have around 10 x 1 TB SATA drives. Would it be a RAID 10,  or RAID 5.  I guess backups would be more write intensive than read.
RAID configuration