Review Session for Fourth QuizBlue File SystemSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12PergamumSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33FARSITESlide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56FarsiteSlide 58ZyzzyvaSlide 60Slide 61Slide 62Slide 63Slide 64Slide 65FAWNSlide 67Slide 68Slide 69Slide 70Slide 71Slide 72Slide 73Slide 74Slide 75Slide 76Slide 77Slide 78Review Session forReview Session forFourth QuizFourth QuizJehan-François PârisJehan-François PârisSummer 2011Summer 2011Blue File SystemBlue File SystemAccording to the designers of the Blue System what are the two limitations of flash drives?Blue File SystemThey can be lost.It is hard to keep them synchronizedBlue File SystemThe Blue File System is said to have a dynamic storage hierarchy. What does it mean?Blue File SystemThe ranking of the storage devices in the storage hierarchy depends on their states.A disk that is powered down will have a lower priority in the hierarchy than the remote server A disk that is powered up will have a higher priority than the same serverBlue File SystemHow does the Blue file system operate its device write queues?Blue File SystemIt empties them when it flushes them to disk.Much more could be said.Blue File SystemExplain how the Blue file system saves energy by aggregating writes to local disks.Blue File SystemAggregating writes to local disks saves energy by amortizing disk power state transitions across multiple writes.Blue File SystemTrue or false:Most of the Blue FS functionality is handled by a user-level server.Blue File SystemTruePergamumPergamumPergamumPergamumWhat equipment failures can be What equipment failures can be corrected by corrected by intratome redundancyintratome redundancy? ?PergamumPergamumIrrecoverable read errorsIrrecoverable read errorsPergamumPergamumWhat would be the main drawback of a What would be the main drawback of a Pergamum system havingPergamum system havingPlenty of Plenty of intratome redundancyintratome redundancy but butNo No intertome redundancyintertome redundancy? ?PergamumPergamumIt would not tolerate full disk failures It would not tolerate full disk failuresPergamumPergamumHow do intradisk parity blocks contribute How do intradisk parity blocks contribute to to reduce the power consumptionreduce the power consumption of of the system? the system?PergamumPergamumThey allow the local recovery of bad They allow the local recovery of bad blocks without having to power up other blocks without having to power up other tomestomesPergamumPergamumWhat are the two main functions of What are the two main functions of Pergamum Pergamum digital signaturesdigital signatures??Where are they stored? Where are they stored?  Why?Why?PergamumPergamumTheir two main functions areTheir two main functions areTo verify the integrity of the tome’s To verify the integrity of the tome’s contentscontentsBy exchanging them with other By exchanging them with other Pergamum tomes, to verify the Pergamum tomes, to verify the integrity of distributed data.integrity of distributed data.PergamumPergamumWhere are they stored? Where are they stored?  Why?Why?PergamumPergamumThey are stored in a small flash drive so They are stored in a small flash drive so they can be consulted without powering they can be consulted without powering the tome’s hard drive.the tome’s hard drive.PergamumPergamumWhat is What is disk scrubbingdisk scrubbing? ?PergamumPergamumDisk scrubbing periodically verifies that Disk scrubbing periodically verifies that a given range of disk blocks can be a given range of disk blocks can be retrieved and reconstitutes the contents retrieved and reconstitutes the contents of the blocks that it could no access of the blocks that it could no access due to an irrecoverable read error. due to an irrecoverable read error.PergamumPergamumWhich feature of Pergamum reduces Which feature of Pergamum reduces the need for frequent full-disk scrubs?the need for frequent full-disk scrubs?PergamumPergamumPergamum intratome parity reduces Pergamum intratome parity reduces the need for frequent disk scrubs as it the need for frequent disk scrubs as it provides an additional way to provides an additional way to reconstitute the contents of the blocks reconstitute the contents of the blocks that caused irrecoverable read errors.that caused irrecoverable read errors.PergamumPergamumHow does Pergamum reconstitute data How does Pergamum reconstitute data contained on a tome that failed?contained on a tome that failed?PergamumPergamum1.1.Pergamum replaces the failed tome by Pergamum replaces the failed tome by a new tomea new tome2.2.One after the other, each tome in the One after the other, each tome in the same parity stripe as the failed tome same parity stripe as the failed tome sends its contents to the new tomesends its contents to the new tomePergamumPergamumWhy?Why?PergamumPergamumTo avoid powering up too many tomes To avoid powering up too many tomes at the same timeat the same timePergamumPergamumHow does the system’s workload—and How does the system’s workload—and intended use(s)-- affect the tradeoffs to intended use(s)-- affect the tradeoffs to consider when deciding the right amount consider when deciding the right amount of intra-disk and inter-disk redundancy in of intra-disk and inter-disk redundancy in a storage system?a storage system?PergamumPergamumIntra-disk redundancy saves energy in Intra-disk redundancy saves energy in archival file systems because it allows larchival file systems because it allows local ocal reconstructionreconstruction of irrecoverable read errors of irrecoverable read errorsWe might prefer using more inter-disk We might prefer using more inter-disk redundancy in conventional file systems as redundancy in conventional file systems as inter-disk redundancy protects data against inter-disk redundancy protects data against both both irrecoverable read errorsirrecoverable read errors andand disk disk failuresfailures..FARSITEFARSITEFARSITEFARSITEHow does FARSITE store users’ secret keys?Why?FARSITEFARSITEFARSITE