ABCs of z/OS System Programming Volume 3 - IBM Redbooks

8.4 Enterprise Storage Server (ESS)
Two 6-way RISC processors (668 MHZ)
4.8 GB/sec of aggregate bandwidth
Up to 32 ESCON/SCSI/mixed
Up to 16 FICON and FCP channels
Up to 64 GB of cache
2 GB of NVS cache
18.2/36.4/72.8/145.6 GB capacity disk options
Up to 55.9 TB capacity
8 x 160 MB/sec SSA loops
10,000 rpm and 15,000 rpm disk options
Connects to SAN
RAID-5 or RAID-10
Figure 8-4 Enterprise Storage Server model 800
Enterprise Storage Server (ESS)
The IBM Enterprise Storage Server (ESS) is a high performance, high availability capacity
storage subsystem. It contains two six-way RISC processors (668 MHZ) with up to 64 GB
cache and 2 GB of non-volatile storage (NVS) to protect from data loss during power outages.
Connectivity to IBM mainframes is through up to 32 ESCON channels and up to 16 FICON
channels. For other platforms, such as IBM System i®, UNIX, or NT, the connectivity is
through up to 32 SCSI interfaces.
Cache
Cache is used to store both read and write data to improve ESS performance to the attached
host systems. There is the choice of 8, 16, 24, 32, or 64 GB of cache. This cache is divided
between the two clusters of the ESS, giving the clusters their own non-shared cache. The
ESS cache uses ECC (error checking and correcting) memory technology to enhance
reliability and error correction of the cache. ECC technology can detect single- and double-bit
errors and correct all single-bit errors. Memory scrubbing, a built-in hardware function, is also
performed and is a continuous background read of data from memory to check for correctable
errors. Correctable errors are corrected and rewritten to cache. To protect against loss of data
on a write operation, the ESS stores two copies of written data, one in cache and the other in
NVS.
Chapter 8. Storage management hardware 453