Netchannel: A VMM-level Mechanism for Continuous, Transparent Device Access During VM Migration

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Netchannel A VMM-level Mechanism for Continuous,
Transparent Device Access During VM Migration

• Sanjay Kumar
• PhD Candidate, Georgia Tech
• In Collaboration with
• Prof. Karsten Schwan

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I/O Location Transparency

• Accessing I/O devices irrespective of location
• Transparency required for legacy systems
• An important objective of I/O virtualization
• VM migration, remote device access
• Current I/O virtualization lacks this feature
• I/O virtualization layer expects local device
• Usually relies on other technologies
• Hardware, e.g. FC SAN (costly)
• Software, e.g. iSCSI, NFS (non-transparent,
  inefficient)
• Need transparent and efficient VMM level mechanism

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Location Transparency Benefits

• Virtual device migration
• Device hot-swapping
• Remote device access

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Virtual Device Migration (VDM)

• Continued access to I/O devices after live VM
  migration
• Migrating virtual device state along with VMs
• Issues
• Handling pending I/O transactions
• Minimizing device state transfer time

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Device Hot-Swapping (DHS)

• Dynamically changing VMs virtual device to
  physical device mapping
• For performance, reliability
• Issues
• Consistent state transfer b/w the two devices
  with minimal service disruption
• Migrating potentially huge amount of data

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Transparent Device Remoting (TDR)

• Transparently providing VMs with access to remote
  devices
• Utilizing the existing I/O virtualization
  infrastructure
• Issues
• High-level semantics become complex
• Data-sharing, caching

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Utility of Transparent Device Remoting
Handheld
Backup DVD-drive
Server
Network
Compute Blade
Compute Blade
I/O Blade
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Netchannel Software Architecture
Local Machine
Remote Machine
Service VM
Service VM
Guest VM
Network
Device Virtuali- zation
Mid- Point
Dev Client
Device Server
device driver
Hypervisor
Hypervisor
device
vdevice
device
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Virtual Device Migration
Machine M1
Remote Machine
Service VM
Guest VM
Operating System
Device Virtualization
Network
Mid- Point
device driver
Hypervisor
Device Server
VM Migration
Netchannel
Machine M2
Service VM
Device
Device Virtualization
Mid- Point
Hypervisor
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Netchannel vs. Resubmit Latency
Pending Reqs. Incomplete Reqs. Netchannel Latency Resubmit Latency
5 0 1.94 ms 23.43 ms
12 0 2.74 ms 40.29 ms
16 1 12.93 ms 45.01 ms
23 5 23.41 ms 81.23 ms
26 2 16.69 ms 85.46 ms
32 7 29.24 ms 96.90 ms
Time taken in handling pending disk requests
during live VM migration
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Device Hot-Swapping
Device1
Network
Machine M1
Service VM
Guest VM
Device Replication
Device Virtualization
Mid- Point
device driver
Hypervisor
Device2
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Transparent Device Remoting
Local Machine
Remote Machine
Service VM
Service VM
Guest VM
Network
Device Virtualization
Mid- Point client
Mid- Point server
Device Virtualization
device driver
Hypervisor
Hypervisor
device
vdevice
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Implementation

• Netchannel implemented in Xen
• Works for block and USB devices
• Provides access to remote disks (RVBD)
• Access granularity at USB port level (RUSB)
• Tested for bulk and isochronous devices

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Transparent Device Remoting

• Testbed description
• Two Dell Poweredge 2650s connected through a
  gigabit switch
• Each machine has 2.28 GHz, 2-way HT Xeon CPUs and
  2 GB RAM
• Iozone file I/O benchmarks used

Write throughput of block devices
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Netchannel Latency
Latency incurred by one block device request
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Virtual Device Migration and Device Hot-Swapping
Migrated MySQL Server
B
VM
Client1
I
Apache Httpd
Client2
VM
A
II
Jakarta Tomcat Servlet Server
Original MySQL Server
MySQL server migration in RuBIS online auction
benchmark
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RuBIS DB VM migration and Hot-swapping
Effect on RUBiS Throughput due to MySQL Server
Migration
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Ongoing and Future Work

• Disk hot-swapping for reliability
• Managing VM migration
• Virtualizing mobile devices

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Netchannel Summary

• Handling I/O devices during
• Live VM migration
• Device hot-swapping
• Remote device access
• Provides a transparent and cost-effective solution

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Questions/Comments

• ksanjay_at_cc.gatech.edu
• http//www.cc.gatech.edu/ksanjay