Which set will disable write cache on a CX?
A.
One (1) SPS enabled and one (1) SPS faulted
B.
One (1) SP functioning and one (1) SP faulted
C.
Drive 0_0_4 faulted and “HA cache” checked
D.
Drive 0_0_2 faulted and “HA cache Vault” checked
E.
Drive 0_0_1 faulted and “HA cache Vault” checked
Explanation:
Given the Vault Drive Private Space Structure shown below, a fault on any of the vault disks 0-4 where “HA cache Vault” is checked would disable the cache.
In Firmware Release 12 for CX series systems, and option has been added to the storage system properties dialog box Caching tab. If
HA Cache Vault is selected (this is the default), write caching is disabled if a single vault disk fails. If this option is deselected, write
caching remains active when a single disk fails. Important: if write caching is active when a single cache vault disk fails, data is at risk
if another cache vault disk should fail and power is lost (triple failure) {pg 24, EMC Clariion Fibre Channel Storage Fundamentals
10/31/2003}
Given the question as is, we would state that B is the correct answer. One faulted SPS (standby power supply) will not disable cache so long as there is a functioning one left.The RAID engine disables the cache if the following conditions are not met:
1. An SPS must be present, and it must be fully charged
2. All vault drives must be present; they cannot be faulted or rebuilding (if the Highly Available vault setting is selected)
3. Both SPs must be present and functional
4. Both power supplies must be present in the DPE/SPE
5. Both fan packs must be present in the DPE/SPE
6. The DPE/SPE and all DAEs must have two nonfaulted link control cards each