GFCache: A Greedy Failure Cache Considering Failure Recency and Failure Frequency for an Erasure-Coded Storage System

In the big data era,data unavailability,either temporary or permanent,becomes a normal occurrence on a daily basis.Unlike the permanent data failure,which is fixed through a background job,temporarily unavailable data is recovered on-the-fly to serve the ongoing read request.However,those newly revived data is discarded after serving the request,due to the assumption that data experiencing temporary failures could come back alive later.Such disposal of failure data prevents the sharing of failure information among clients,and leads to many unnecessary data recovery processes,(e.g.caused by either recurring unavailability of a data or multiple data failures in one stripe),thereby straining system performance.To this end,this paper proposes GFCache to cache corrupted data for the dual purposes of failure information sharing and eliminating unnecessary data recovery processes.GFCache employs a greedy caching approach of opportunism to promote not only the failed data,but also sequential failure-likely data in the same stripe.Additionally,GFCache includes a FARC(Failure ARC)catch replacement algorithm,which features a balanced consideration of failure recency,frequency to accommodate data corruption with good hit ratio.The stored data in GFCache is able to support fast read of the normal data access.Furthermore,since GFCache is a generic failure cache,it can be used anywhere erasure coding is deployed with any specific coding schemes and parameters.Evaluations show that GFCache achieves good hit ratio with our sophisticated caching algorithm and manages to significantly boost system performance by reducing unnecessary data recoveries with vulnerable data in the cache.

A meta-analysis of randomized trials of maintenance bacillus Calmette-Guerin instillation efficacy against recurrence of T1G3 bladder tumor

Meta-analysis was used to determine whether maintenance intravesical bacillus Calmette-Guerin(BCG)could reduce recurrence after transurethral resection of tumor 1 grade 3(T1G3)superficial bladder cancer.All available published data of randomized clinical trials comparing transurethral resection plus intravesical BCG to either resection alone or resection plus another treat-ment on the treatment results in patients with superficial bladder cancer of T1G3 were selected for analysis.Both the fixed effects model and random effects model were applied,and the odds ratio(OR)with its 95%confidence interval(CI)was used as the effect size estimate.Sensitivity analysis and publication bias determination were performed by funnel plots and comparing ORs of different models.Within the follow-up period,375 of 915(41.0%)BCG-treated patients and 332 of 733(45.3%)non-BCG-treated patients developed tumor recurrence.In the combined results,a statistically signifi-cant difference in the ORs for tumor recurrence between the two treatment groups was found(randomized model combined effect OR 0.58,95%CI 0.41 to 0.83,P 50.003).The stratified meta-analysis did not show any statistically significant confounding effects on the results when strati-fied by BCG strains.The randomized model combined effect OR of Pasteur F and other strains were 0.50(95%CI 0.26 to 0.95,P 50.04)and 0.63(95%CI 0.40 to 0.99,P 50.04),respectively.Therefore,we came to the conclu-sion that adjuvant maintenance instillation BCG com-bined with transurethral resection of bladder tumor(TURBT)is an effective conservative treatment for pre-venting recurrence of T1G3 bladder cancer.