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How should the three tiers for the FAST VP pool be configured?

You have been tasked with designing the storage layout for a VNX7600 array. VMware hosts will
attach to the array using two HBAs and two Fibre Channel switches. The array will have FAST VP,
SnapView, and FAST Cache installed.
The customer wants to configure FAST Cache with a capacity of 2000 GB. They also want to put
as many drives as possible into a single FAST VP pool while still being able to use SnapView.
Snapshots will be taken each day of 10 x 1 TB LUNs and will be used for backups to tape. Once
the backups complete, the snapshots will be destroyed. The customer insists on using SnapView
due to the backward compatibility with their scripts. The source LUNs will produce less than 20%
change daily.
The array has the following hard drives installed:
— 31 X 200 GB Flash hard drives
— 34 X 600 GB 15K SAS hard drives
— 17 X 2 TB 7.2K NL-SAS hard drives
The entire design should follow EMC best practices.
Click on the calculator icon in the upper left corner.
How should the three tiers for the FAST VP pool be configured?

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A.
Flash Tier 10 drives RAID 5 SAS Tier 24 drives RAID 1/0 NL-SAS Tier 16 drives RAID 6

B.
Flash Tier 10 drives RAID 5 SAS Tier 25 drives RAID 5 NL-SAS Tier 15 drives RAID 5

C.
Flash Tier 20 drives RAID 1/0 SAS Tier 30 drives RAID 5 NL-SAS Tier 15 drives RAID 5

D.
Flash Tier 20 drives RAID 5 SAS Tier 32 drives RAID 1/0 NL-SAS Tier 16 drives RAID 6

4 Comments on “How should the three tiers for the FAST VP pool be configured?”

  2. kerkael says:

    FAST Cache of 2TB requires 20×200 GB Flash Drives in RAID 1
    This leaves only 10×200 GB Flash Drives for the FAST VP Flash Tier.
    Remains 1 for the Spare, answer is A or B.

    NL-SAS is much best practice in RAID 6 than in RAID 5. But this makes SAS in RAID 1/0 for 24 drives against 25 in RAID 5 ! So what ? Nobody said what capacity is expected for this tier … you can make it faster and more reliable with RAID 1/0 than with RAID 5.

    Remains 10 SAS drives … 1 for spare … other 9 for what ?




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  3. JC says:

    The answer is A. To answer Kerkael’s question, “other 9 for what?”. Those 9 would support the Snapview requirement for a Reserved LUN Pool (RLP). In this case best practice would be 20 – 50GB LUNs for the RLP. So the 9 extra SAS drives could be configured in a 8+1 R5 RAID group.




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