Seagate ST3146855LC Economies of Capacity and Speed: Choosing the most cost-ef - Page 1

TP-525 • From: Seagate Global Product Marketing • May 2004 Technology Paper Economies of Capacity and Speed: Choosing the most cost-effective disc drive size and RPM to meet IT requirements Introduction IT departments are under growing pressure to find the most cost-effective means to meet their escalating data storage requirements, including disc drive capacity and performance. Today's storage systems must hold ever-increasing amounts of data, achieve input/output (I/O) performance goals, meet client response-time expectations and minimize physical space (U or ft3) requirements. Furthermore, IT professionals must ensure their storage systems are reliable-maximizing system availability while minimizing drive failures, the number of RAID rebuilds and RAID rebuild time. All of these factors can come into play when determining the optimal capacity and speed of a system's disc drives. In this paper we will discuss a variety of factors that impact the choice of disc drive capacity and speed for systems that offer a choice between 3.5-inch 10K-RPM drives and 3.5-inch 15K-RPM drives. Let us start by looking at the current trend in drive purchase decisions. While IT departments often speak of buying drives on the basis of cost/capacity (price per GB), the majority of drives they will actually purchase are 36GB 10K (lowest price box cost), as opposed to 146GB 15K (highest initial acquisition price/GB) or 300GB 10K (lowest price per GB). Were cost/capacity truly the dominant purchase criterion used by IT departments, they would instead be buying 300GB 10K drives (see Figure 1). 350 Capacity 300 300 of 10K 250 Offered 200 Gbytes 150 146 100 50 36 73 0 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 2001 2002 2003 2004 2005 Calendar Year Figure 1. IT departments are not buying the lowest cost/GB drives. Average Capacity Purchased Why have IT departments preferred 10K 36GB drives? The history of disc drives and other system component offerings will shed some light on this.