liuba@proton.lcs.mit.edu (Liuba Shrira) (03/27/91)
Archive-name: os/research/pm-lazy-replication/1991-03-26 Archive: mintaka.lcs.mit.edu:/pub/pm/lazyrep.PS [18.26.0.36] Original-posting-by: liuba@proton.lcs.mit.edu (Liuba Shrira) Original-subject: Re: lazy replication Reposted-by: emv@msen.com (Edward Vielmetti, MSEN) Ken Birman compares the performance of ISIS with that of the Lazy Replication scheme developed by Ladin, Liskov and Shrira at MIT. I would like to make a couple of points about Ken's note. First, the Lazy Replication paper that appeared in PODC 90 does not contain any performance data. The data appear in MIT technical report MIT/LCS/TR-484 authored by Ladin, Liskov, Shrira, and Ghemawat. People interested in Lazy Replication and its performance can send me a note and I will send a hard copy of the paper. Alternatively, a postscript version of the paper can be obtained via anonymous ftp from mintaka.lcs.mit.edu (18.26.0.36) as pub/pm/lazyrep.PS. The second point concerns the performance data themselves. Our paper describes an experiment designed to evaluate the cost of Lazy Replication: it compares the response time and request processing capacity of a prototype replicated server implemented using our replication scheme with that of comparable nonreplicated server. The point of our data is the comparison between the two implementations rather than how fast the replicated implementation ran. We used the Argus system as the implementation platform for the experiments, so our system does not perform as well as it could. For example, all client interactions with the server occur within atomic transactions even though transactions are not needed in our method. We were pleasantly surprised, therefore, to hear that our response times compare so favorably with those of the highly engineered ISIS system! Liuba Shrira liuba@lcs.mit.edu