Disaster recovery in cloud computing: a survey <s> Taiji <s> Increasing performance of CPUs and memories will be squandered if not matched by a similar performance increase in I/O. While the capacity of Single Large Expensive Disks (SLED) has grown rapidly, the performance improvement of SLED has been modest. Redundant Arrays of Inexpensive Disks (RAID), based on the magnetic disk technology developed for personal computers, offers an attractive alternative to SLED, promising improvements of an order of magnitude in performance, reliability, power consumption, and scalability. This paper introduces five levels of RAIDs, giving their relative cost/performance, and compares RAID to an IBM 3380 and a Fujitsu Super Eagle. <s> BIB001 </s> Disaster recovery in cloud computing: a survey <s> Taiji <s> Hypervisor-based fault tolerance (HBFT), which synchronizes the state between the primary VM and the backup VM at a high frequency of tens to hundreds of milliseconds, is an emerging approach to sustaining mission-critical applications. Based on virtualization technology, HBFT provides an economic and transparent fault tolerant solution. However, the advantages currently come at the cost of substantial performance overhead during failure-free, especially for memory intensive applications. This paper presents an in-depth examination of HBFT and options to improve its performance. Based on the behavior of memory accesses among checkpointing epochs, we introduce two optimizations, read-fault reduction and write-fault prediction, for the memory tracking mechanism. These two optimizations improve the performance by 31 percent and 21 percent, respectively, for some applications. Then, we present software superpage which efficiently maps large memory regions between virtual machines (VM). Our optimization improves the performance of HBFT by a factor of 1.4 to 2.2 and achieves about 60 percent of that of the native VM. <s> BIB002
Taiji BIB002 ) is a Hypervisor-Based Fault Tolerant (HBFT) prototype which uses a mechanism similar to Remus. However, instead of Remus which uses separated local disk for replication, Taiji uses a Network Attach Storage (NAS). Shared storage may become a single point and cause a weakness of this method, so RAID BIB001 or commercial NAS (Synology, online) solution should be deployed. On the other hand, because of using shared storage, the need of synchronizing is decreased and also file system state is maintained in the event of disaster.