(Btw that's why it seems you can't define RAID 10 for numbers of disks other than multiples of 4, or multiple of 6 when using more than 3 disks.) Nobody seems to know what the the advantage of such a 'RAID 100' could be, the only thing that seems to be for sure is that it has significant negative impact on performance compared to a good old RAID 10 (that LSI for whatever reason calls RAID 1). Whatever you configure as RAID 10 in the LSI meaning of the term, seems to be more something like a 'RAID 100', i.e., every 'span' is it's own RAID 10, and these spans will be put together as a RAID 0. I can confirm that it does mirroring and striping exactly the way I would expect it for a RAID 10, in my case for a 6 disk array and a 16 disk array. It seems that LSI decided to introduce their own crazy terminology: When you really want a RAID 10 (as defined since ages), you need to choose RAID 1 (!). TL:DR: use the second configuration: It is more robust. As a result, RAID 10 can also be more energy-intensive. However, RAID 5 only requires 3 drives for striping and parity, while RAID 10 requires a minimum of 4 drives to properly set up mirrored striping. That is a lot better then in the previous case (which was 4/7th, or 57%). RAID 5 and RAID 10 offer strong combinations of efficiency and redundancy, with many users favoring RAID 10 for pure performance. Now the other setup, with a stripe of 4 mirrors.Ĩ5% chance that the array is still working. The chance that a second drive fails in the wrong span is 4/7 th (4 drives left in the working span, each of which can fail) and only 3/7 th that is fails in the span which is already down. If the second drive happens in the other span/stripe: If the drive fails in the the same span/stripe then you have the same result as 1 drive lost. If any drives fails in a stripe then that stripe of lost.ġ drive lost -> Working in degraded mode. Your first setup is a mirrored pair of 4 drive stripes. I think your choice should be obvious after this. Read the part in the link I posted where it states:

Match this to your setups (both of them labeled as RAID 10 in your text). Notice the difference between RAID 10 and RAID 01. First off all, see this post: What are the different widely used RAID levels and when should I consider them

Macdrive 10 raid disk utility