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RAID Arrays

RAID Arrays. Module 1.3. Case Study 1: Business Profile. Acme Telecom is involved in mobile wireless services across the United States and has about 5000 employees worldwide. This company is Chicago based and has 7 regional offices across the country.

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RAID Arrays

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  1. RAID Arrays Module 1.3

  2. Case Study 1: Business Profile Acme Telecom is involved in mobile wireless services across the United States and has about 5000 employees worldwide. This company is Chicago based and has 7 regional offices across the country. Although Acme is doing well financially, they continue to feel competitive pressure. As a result, the company needs to ensure that the IT infrastructure takes advantage of fault tolerant features.

  3. Case Study 1: Current Situation/Issues (1) • The company uses a number of different applications for communication, accounting, and management. All the applications are hosted on individual servers with disks configured as RAID 0. • All financial activity is managed and tracked by a single accounting application. It is very important for the accounting data to be highly available. • The application performs around 15% write operations, and the remaining 85% are reads. • The accounting data is currently stored on a 5-disk RAID 0 set. Each disk has an advertised formatted capacity of 200 GB, and the total size of their files is 730 GB. • The company performs nightly backups and removes old information—so the amount of data is unlikely to change much over the next 6 months.

  4. Case Study 1: Current Situation/Issues (2) • The company is approaching the end of the financial year and the IT budget is depleted. Buying even one new disk drive will not be possible. • How would you suggest that the company restructure their environment? • You will need to justify your choice based on cost, performance, and availability of the new solution.

  5. Case Study 1: Solution (1) • A 200 GB disk holds only 186.3 GB of user data. The total size of customer data is 730 GB, which will fit (barely) on 4 disks. We can therefore consider a solution which uses parity-based RAID – RAID 3, RAID 4, or RAID 5. • RAID 3 is useful only in environments where data access will be in large, sequential blocks, so it is excluded here. • RAID 4 is a poorer solution than RAID 5, so it is excluded. • RAID 5 is the only remaining solution that will not require the purchase of extra disks. Because the proportion of writes does not exceed 25 %, RAID 5 should perform reasonably well. We recommend that the disks be reconfigured as a RAID 5 set.

  6. Case Study 1: Solution (2) • RAID level to use: RAID 5 • Advantages: Low cost of data protection • Disadvantages: • Only medium performance – in this environment it will not be a major factor • High overhead if a disk fails

  7. Case Study 2: Business Profile Acme Telecom is involved in mobile wireless services across the United States and has about 5000 employees worldwide. This company is Chicago based and has 7 regional offices across the country. Although Acme is doing well financially, they continue to feel competitive pressure. As a result, the company needs to ensure that the IT infrastructure takes advantage of fault tolerant features.

  8. Case Study 2: Current Situation/Issues (1) • The company uses a number of different applications for communication, accounting, and management. All the applications were hosted on individual servers with disks configured as RAID 0. • The company changed the RAID level of their accounting application based on your recommendations 6 months ago. • It is now the beginning of a new financial year and the IT department has an increased budget. You are called in to recommend changes to their database environment.

  9. Case Study 2: Current Situation/Issues (2) • You investigate their database environment closely, and observe that the data is stored on a 6-disk RAID 0 set. Each disk has an advertised formatted capacity of 200 GB and the total size of their files is 900 GB. The amount of data is likely to change by 30% over the next 6 months and your solution must accommodate this growth. • The application performs around 40% write operations, and the remaining 60 % are reads. The average size of a read or write is small, at around 2 KB.

  10. Case Study 2: Current Situation/Issues (3) • How would you suggest that they restructure their environment? • A new 200 GB disk drive costs $1000. The controller can handle all commonly used RAID levels, so will not need to be replaced. • What is the cost of the new solution? • Justify your choice based on cost, performance, and data availability of the new solution.

  11. Case Study 2: Solution (1) • Each 200 GB drive can hold 186.3 GB of data. There is currently 900 GB of data, which will increase to 1170 GB in the next 6 months. That amount of data will fit on 7 disks, with space left over. • The environment uses a high proportion of writes, so parity-based RAID is not an option. RAID 1 will not allow enough space, so our choices are limited to RAID 0+1, or RAID 1+0. • From the class discussion, we rule out RAID 0+1, leaving only RAID 1+0. This RAID level uses mirroring, so for the 1170 GB of data, we need 7 disk pairs – 14 disks. We already have 5 disks, so need to purchase an additional 9, for a total cost of $9000.

  12. Case Study 2: Solution (2) • RAID level to use: RAID 1+0 • Advantages: Excellent protection, very good performance in environments with a high proportion of writes. Minimal disruption in the event of a disk failure. • Disadvantages: Highest cost (along with RAID 1 and RAID 0+1) of all RAID solutions

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