And now comes another big table showing the controller performance in WriteBack mode:
Here are the graphs illustrating it, take a look:
Note that even when the workload is linear, RAID 1 array is a little faster than a single HDD. In other words, even in this mode the controller driver distributes the read requests between the two HDDs of the mirrored pair.
When the workload reaches 16 requests, we see that RAID 1 array is always a little faster than a single drive. Even in RandomWrite! RAID 01 array also looks not bad at all, though it yielded a little bit to a two-disk RAID 0 in RandomWrite.
With the workload of 256 requests, the picture doesn’t change that much: everything the controller could optimize, has already been done.
At first glance the performance of different array types during WriteThrough and WriteBack caching varied a little bit. But how big was this difference? Let’s try to compare the performance of all arrays in different caching modes.