However, the shared cache hit ratios reported in Figure 2 are conservative in three respects. First, all hits reported are due exclusively to sharing of objects among different clients . Second, a large, unified shared cache would likely yield additional temporal hits in practice, since per-client caches are not infinite, and the most active clients can receive a larger portion of the shared cache at any given time. The workloads from the Small trace experienced the highest overall hit ratios due to repeated references to non-shared objects from individual clients. The relatively low temporal hit ratio in the large traces reflects the filtering of the reference streams by browser caches and lower-level proxies.
Small caches are useless for sharing.
The largest traces exhibit the lowest hit ratios for small cache sizes, because objects live in the cache for only a short time before they are evicted. Only large caches yield the full benefit of shared object references from multiple clients. More users, more sharing. Given sufficiently large caches, traces from the larger user communities exhibited the highest peak hit ratios, and the greatest benefit from a shared cache. The benefit to smaller user communities is more modest.