You benefit from putting commit log on separate drive only if this drive is an isolated spinning device. EC2 ephemeral is a virtual device, so I don't think it makes sense to put commit log on a separated drive. I would build raid0 from 4 drives and put everything their. But it would be interesting to compare different configurations.

Thank you,
   Andrey


On Mon, Sep 2, 2013 at 7:11 PM, Renat Gilfanov <grennat@mail.ru> wrote:
Hello,

I'd like to ask what is the best options of separating commit log and data on Amazon m1.xlarge instance, given 4x420 Gb attached storages and EBS volume ?

As far as I understand, the EBS is not the choice and it's recomended to use attached storages instead.
Is it better to combine 4 ephemeral drives in 2 raid0 (or raid1 ?), and store data on the first and commit log on the second? Or may be trying other combinations like 1 attached storage for commit log, and 3 others grouped in raid0 for data?

Thank you.