Battery backup with a hardware RAID controller is fantastic for increasing write performance of a RAID array. You can literally call flush() on a file, and it returns almost instantly, so if you are doing this a lot it makes sense to either use one of these or a solid state drive. If the system is well-maintained, then the chances of it failing are "small". However, the whole ethos of ZFS is that it wants to manage individual discs itself.
With regard to other hardware, there are certainly devices out there that will ignore flush requests, in the name of performance. These are usually consumer-grade devices. If you're paying extra for an enterprise-grade drive from a reputable manufacturer, you should be fine.
Battery backup with a hardware RAID controller is fantastic for increasing write performance of a RAID array. You can literally call flush() on a file, and it returns almost instantly, so if you are doing this a lot it makes sense to either use one of these or a solid state drive. If the system is well-maintained, then the chances of it failing are "small". However, the whole ethos of ZFS is that it wants to manage individual discs itself.
With regard to other hardware, there are certainly devices out there that will ignore flush requests, in the name of performance. These are usually consumer-grade devices. If you're paying extra for an enterprise-grade drive from a reputable manufacturer, you should be fine.