TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

20
6/5/2008 1 TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time Authors: Qing Yang,Weijun Xiao,Jin Ren University of Rhode Island Presented By: Anuradharthi T

description

TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time. Authors: Qing Yang,Weijun Xiao,Jin Ren University of Rhode Island Presented By: Anuradharthi T. Outline. Introduction Background Related Work TRAP- 4 Architecture Results Conclusion. - PowerPoint PPT Presentation

Transcript of TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

Page 1: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 1

TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

Authors: Qing Yang,Weijun Xiao,Jin Ren University of Rhode Island

Presented By: Anuradharthi T

Page 2: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 2

Outline Introduction Background Related Work TRAP- 4 Architecture Results Conclusion

Page 3: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 3

IntroductionRAID Architecture

- Most prominent architecture advance in disk I/O

systems

- In use for more than two decades

- Types of RAID: RAID1- provides 2N data redundancy to protect data RAID3, 4 & 5- store data in parity stripes across

multiple disks to improve space

efficiency & performance

Page 4: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 4

RAID Architecture Advantages:

- Can recover data from more than one disk failure- Improves data reliability

Disadvantages:- Recovery not possible when damaged data are not confined to 1 or 2 disks- Accounts for 60% to 80% of data losses- Examples of such damages are: software defects,

virus attacks, power failure or site failure

Page 5: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 5

Solution

Timely Recovery to Any Point-in-time(TRAP)- Keep log of all previous versions of changed data

blocks in time sequence- Utilizes a fast & simple encoding scheme

=> less space- Provides faster data recovery to any-point-in-time due to

drastically smaller amount of storage space used =>improved performance

- Thus achieves an optimal space & performance characteristics

Page 6: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 6

BackgroundRecovery of data in real world is measured by ‘2’

key parameters:1. RPO (Recovery Point Objective)

- measures maximum acceptable age of data at time of outage

2. RTO (Recovery Time Objective)

- maximum acceptable length of time to resume normal data processing operations after an outage

Page 7: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 7

Classification of storage architecture Storage architectures are capable of recovering

data upon an outage Based on the 2 key parameters

TRAP-1 TRAP-2 TRAP-3 TRAP-4

Page 8: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 8

Related work TRAP-1

Uses periodical backups & snapshots Time consuming & degrades application performance Data transferred to tapes or disk for backup

TRAP-2 Performs file versioning that records a history of changes to files Versioning has to be done manually Have controllable RTO & RPO File system dependent

TRAP-3 Keep a log of changed data for each data block in a time sequence

(time stamps) Continuous Data Protection (CDP) Huge amount of storage space required

Page 9: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 9

TRAP-4 Architecture

Keeps a log of parities as a result of each write on the block Suppose a host writes into data block with logic address Ai

that belongs to a data stripe (A1,A2….Ab….An) RAID controller perform the parity calculation as follows:

Where, PT(k) – new parity for corresponding stripe

Ai(k) – new data for data block Ai

Ai(k-1) – old data of data block Ai

PT(k-1) – old parity of the stripe

Page 10: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 10

Optimizing the parity P’T(k)= is appended to the parity log stored in the TRAP disk after a simple encoding Only 5% to 20% of bits inside a data block actually change on a write operation Parity P’T(k) reflects the exact changes at bit level of new write operation on the existing block As a result, this parity block contains mostly zeros with a very small portion of bit stream that is nonzero Thus it can be easily encoded to a small size parity block to be appended to the parity log reducing the amount of storage space

Page 11: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 11

Block Diagram of TRAP-4 design

Page 12: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 12

Recovery on outage Consider the parity log corresponding to a data block, Ai

after a series of write operations. Log contains P’T(k) P’T(k-1) …. P’T(2) P’T(1) with timestamps

T(k), T(k-1), …. T(2) and T(1) associated with parities When an outage occurs at time t1, and we would like to

recover data as at time t0 (t0 < t1)

Note that for all l = 1,2, … r

Page 13: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 13

System Architecture of TRAP-4

Page 14: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 14

Experimental Setup

Page 15: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 15

File System micro benchmarks

Page 16: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 16

Data size comparison

Page 17: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 17

Data Reduction ratio

Page 18: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 18

Retrieval time comparison

Page 19: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 19

Conclusions A new disk array architecture capable of providing

timely recovery to any point-in-time for user data stored in array

Up to 2 orders of magnitude improvements in terms of storage efficiency

Has quick recovery time Provides continuous data protection capability

Page 20: TRAP-Array: A Disk Array Architecture Providing Timely Recovery to Any Point-in-time

6/5/2008 20

Thank You