  Recently, the capital expenditure of flash-based Solid State Driver (SSDs)
keeps declining and the storage capacity of SSDs keeps increasing. As a result,
all-flash storage systems have started to become more economically viable for
large shared storage installations in datacenters, where metrics like Total
Cost of Ownership (TCO) are of paramount importance. On the other hand, flash
devices suffer from write amplification, which, if unaccounted, can
substantially increase the TCO of a storage system. In this paper, we first
develop a TCO model for datacenter all-flash storage systems, and then plug a
Write Amplification model (WAF) of NVMe SSDs we build based on empirical data
into this TCO model. Our new WAF model accounts for workload characteristics
like write rate and percentage of sequential writes. Furthermore, using both
the TCO and WAF models as the optimization criterion, we design new flash
resource management schemes (MINTCO) to guide datacenter managers to make
workload allocation decisions under the consideration of TCO for SSDs. Based on
that, we also develop MINTCO-RAID to support RAID SSDs and MINTCO-OFFLINE to
optimize the offline workload-disk deployment problem during the initialization
phase. Experimental results show that MINTCO can reduce the TCO and keep
relatively high throughput and space utilization of the entire datacenter
storage resources.
