2012
06.18

Notes from TechEd NA 2012 session WSV303:

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One of the traits of the Scale-Out File Server is Transparent Failover for server-server apps such as SQL Server or Hyper-V.  During a host power/crash/network failure, the IO is paused briefly and flipped over to an alternative node in the SOFS.

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Transparent Failover

The Witness Service and state persistence enable Transparent Failover in SMB 3.0 SOFS.  The Witness plays a role in unplanned failover.  Instead of a TCP timeout (40 seconds and causing application issues), speeds up the process.  It tells the client that the server that they were connected to has failed and should switch to a different server in the SOFS.

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NTFS Online Scan and Repair

  • CHKDSK can take hours/days on large volumes.
  • Scan done online
  • Repair is only done when the volume is offline
  • Zero downtime with CSV with transparent repair

Clustered Hardware RAID

Designed for when using JBOD, probably with Storage Spaces.

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Resilient File System (ReFS)

A new file system as an alternative to NTFS (which is very old now).  CHKDSK is not needed at all.  This will become the standard file system for Windows over the course of the next few releases.

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Comparing the Performance of SMB 3.0

Wow! SMB 3.0 over 1 Gbps network connection achieved 98% of DAS performance using SQL in transactional processing.

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If there are multiple 1 Gbps NICs then you can use SMB Multichannel which gives aggregated bandwidth and LBFO.  And go extreme with SMB Direct (RDMA) to save CPU.

VSS and SMB 3.0 File Shares

You need a way to support remote VSS snapshots for SMB 3.0 file shares if supporting Hyper-V.  We can do app consistent snapshots of VMs stored on a WS2012 file server.  Backup just works as normal – backing up VMs on the host.

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  1. Backup talks to backup agent on host. 
  2. Hyper-V VSS Writer reaches into all the VMs and ensures everything is consistent. 
  3. VSS engine is then asked to do the snapshot.  In this case, the request is relayed to the file server where the VSS snapshot is done. 
  4. The path to the snapshot is returned to the Hyper-V host and that path is handed back to the backup server. 
  5. The backup server can then choose to either grab the snapshot from the share or from the Hyper-V host.

Data Deduplication

Dedup is built into Windows Server 2012.  It is turned on per-volume.  You can exclude folders/file types.  By default files not modified in 5 days are deduped – SO IT DOES NOT APPLY TO RUNNING VMs.  It identifies redundant data, compresses the chunks, and stores them.  Files are deduped automatically and reconstituted on the fly.

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REPEAT: Deduplication is not intended for running virtual machines.

Unified Storage

The iSCSI target is now built into WS2012 and can provide block storage for Hyper-V before WS2012. ?!?!?!  I’m confused.  Can be used to boot Hyper-V hosts – probably requiring iSCSI NICs with boot functionality.

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4 comments so far

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  1. Question about HA over SMB. I like the idea that SMB can now host storage for Hyper-V, but I’m unclear on how the HA piece works. It looks like from the session you cluster two file servers together but those two file servers have to have shared storage of some kind. On the 47 minute mark of the session, they show some Cluster-In-A-Box solutions by OEMs that do exactly this.

    My question is, how do you expand on this if you wanted to add more storage later or replicate it to a second array/site? It seems like the shared storage backend requirement will keep you limited in that sense. These seem like the equivalent of a dual controller, active/active array like the HP P2000 or Dell MD3x series that don’t replicate or do network RAID with another array.

    Don’t get me wrong though, VHDs on SMB shares would be super convenient, no more iSCSI configs to worry about!

    • SOFS is aimed at a new type of storage: JBOD attached with SAS Expander cards. You can either scale up (add trays) or scale out (add new clusters).

      If you want site-site replication then you have options:
      1) Don’t use SOFS and pay lot$ of mon€y for an £xpensive multi-site cluster with identical SANs and plenty of low latency networking.
      2) I’d expect the likes of DoubleTake to support CSV via the new filter extensions to allow replication from one location to another. Nothing firm there.
      3) Use Hyper-V Replica which is free and storage agnostic

  2. Would Hyper-V Replica replicate from an iscsi “SAN” to SMB file shares? It looks like it could no problem. I want to move our slow SAN over to our branch datacenter to be a disaster recovery site and build a SMB solution at the main branch.

    • Hyper-V Replica does not replicate storage. It replicates virtual machines from one host/cluster to another host/cluster. Therefore it doesn’t care what storage you are using as long as it’s on the HCL.

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