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A customer wants to configure FAST Cache on their VNX storage system. Their working data set
is 600 GB in size. They plan to have sufficient FAST Cache to hold the working data set. There
are currently no Flash drives in the storage system. The customer wants to follow EMC best
practices.
How can this be achieved?
A.
Four 200 GB Flash drives
B.
Six 200 GB Flash drives
C.
Thirteen 100 GB Flash drives
D.
Fifteen 100 GB Flash drives
First, a spare is required, and RAID 1 is Best Practice so answer can’t be even.
Now, a flash drive can hold 93/100 GB or 186/200 GB of data.
13×100 GB with RAID 1 and spare would only provide for 6*93=558 GB … not enough
15×100 GB with RAID 1 and 1 spare would provide [(15-1)/2]*93=651 GB … which is enough
If you really would not consider the required spare, but still the RAID 1, 4x200GB provides 2×186=372 GB.
If you think RAID 5 + a spare is a good practice, then answer B could give you 4*186=744 GB … but RAID 1 is Fast Cache Best Practice. Forget RAID 5 !
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