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This analysis is based on a configuration of 32 traditional Memcached servers with 32 GB of
memory each. It uses a standard client workload with 1-kB average object size (randomized),
128-kB average key size (randomized), 95% gets (with 1 object per get) and 5% sets. Traditional
Memcached servers, limited by DRAM capacity, only use about 1 Gb of network bandwidth and
only use a small fraction of the Nehalem processors. The high utilization and system balance of
the SanDisk architecture enable the consolidation and the power efficiency of SanDisk parallel
flash memory yields an eight-fold improvement in throughput per watt.
Industry-Leading Data and Service Availability
Web sites increasingly depend on Memcached and key-value stores for top application per-
formance. Failures in this tier can lead to large, unexpected loads on the underlying database,
which can significantly degrade the end-user experience. Membrain provides a comprehensive
set of HA/DR features to ensure a consistent user experience through both planned and
unplanned downtime.
Some SanDisk customers use Membrain as their sole data repository, without a database as the
primary data store. Whether or not this is the case, the high availability provided by Membrain
is a key benefit for many of SanDisk’s customers.
Membrain enables a range of availability options for Memcached and key-value store deploy-
ments. As shown in Figure 9, the Membrain availability extension can reduce the downtime
more than 90% relative to a traditional Memcached cluster.
Figure 10: SanDisk Availability Spectrum
Persistent Caching
All cached data is immediately available, even after a power outage;
Delivers the persistence of flash memory with the performance of DRAM;
Avoids performance-degrading, multi-hour or multi-day cache warm-up periods;
Reduces system downtime by more than 40%.
SSD RAID
Protects from downtime caused by SSD failures and planned SSD maintenance;
Minimizes the capacity overhead required for redundancy.
Reduces system downtime by almost 60%, when combined with Persistent Caching.
Traditional
Memcached
SanDisk availability extensions (Cumulative effect)
Reduction in downtime (%
)
Persistent
Caching
SSD
RAID
Replication &
Failover
10
30
20
0
40
50
60
80
100
90
70
