CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 CS 695 Topics in Virtualization and Cloud Computing Live Migration of Virtual Machines Clark et.al., NSDI 2005

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Aspects of virtual machine migration ● Why big deal? – Live, no process migration-type drawbacks – What are process migration issues ? – Virtual machine managment handle (consolidation etc.) ● What are parameters of migration?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 The pre-copy approach

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Important points ● ARP ● What is ARP? ● Why required? ● Network attached storage ● Why ? ● Reliability guarantee ● What if A's ACK lost?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Pre-copy Optimizations ● Dynamic rate-limiting – Is this required? – Should be ON by default? ● Skip list – Skip pages dirtied in this iteration ● Stun rougue pages ● Free page-cache pages – What is implication?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Pre-copy in action

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Positives ● Well written ● Empirical motivation precedes procedures – e.g., dynamic rate limiting ● Experiments presented with clarity – All graphs readable – Several real workloads consider for evaluation – “performance” implications on application (Fig. 8) ● Realistic problem in the virtualization domain ● All VM technologies support migration

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Negatives ● Section 5.3, dynamic-rate limiting, could have been presented as an algorithm ● Pseudo-random scanning order ● What is the ordering procedure?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Questions #1 ● What is et.al.? ● What is NSDI? ● What is RAID? ● Why is migration-time a parameter? ● What are the resource parameters?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Extensions ● Experiments – Page dirty rate vs. Migration parameters – CPU resource overheads for migration, if no extra CPU at Dom0 then what? ● Ballooning procedure – How much to balloon before migration ? – Time to balloon =, time to migrate ? – f(writeable working set) – Balloon size vs. Migration parameters (for different page dirty rates, working set sizes)

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Post-Copy Based Live Virtual Machine Migration Using Adaptive Pre-Paging and Dynamic Self-Ballooning Michael R. Hines and Kartik Gopalan VEE 2009 what is VEE?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Drawbacks of pre-copy?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Drawbacks of pre-copy? ● Downtime can be high if page dirty rate/writeable working set high – Paper does not quantify this (in motivation)

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Post-copy approach ● Demand Paging + Active push ● + ● Post-copy ● + ● Adaptive pre-paging ● + ● Dynamic self ballooning

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Timeline comparison

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Implications of post-copy approach

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Implications of post-copy approach ● Low downtime, VM up quickly at dest. ● Page-faults go over network ● Number of times each page transmitted = ?fs ● Worst case migration time = ?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Reliability with post-copy ● What is source VM fails? ● What if destination VM fails?

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Pseudo-Paging (for pre-paging and active pushing)

CS 695 Topics in Virtualization and Cloud Computing, Autumn 2012 Dynamic Self Ballooning ● The set_shrinker function ● To clean up dentry cache and the inode cache ● reclaim the pages from the disk cache, then it returns the number of reclaimable pages remaining in the cache ● How does DSB use this?