Read-intensive SSDs are a bit of a marketing term, as all SSDs will easily handle reads. The name refers to the lower write endurance. They will, however, provide the best cost per GB. These SSDs will often only have a write endurance of around 0.3-1 drive writes per day over a five-year period. That is to say that you should be able to write 400 GB a day to a 400 GB SSD and expect it to still be working in five years time. If you write 800 GB a day to it, it will only be guaranteed to last two and a half years. Generally, for most Ceph workloads, this range of SSDs is normally deemed not to have enough write endurance.