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Marius_Gordon's avatar
Marius_Gordon
Level 4
11 years ago

How does mirroring work within Storage Foundation

How does storage foundation mirroring works (technical deep dive)?

How does it sync, Synchronous or asynchronous?

 

In other words, I have a LUN in Datacentre 1 mirrored with a LUN in  Datacentre 2.

Datacentre 2 is 50KM away from Datacentre 1. (Just an example)

Will this slow down the system performance? 

 

business continuity
Configuring
Performance
Storage Foundation for Windows
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Windows Server (2003-2008)
  • mikebounds's avatar
    mikebounds
    11 years ago

    Storage foundation mirroring across sites works by have 2 (or more) SAN attached arrays and SF on the node that does the writes, writes to LUNs in both arrays synchronously (i.e the other node at the other site is NOT involved in the write and the node at the other site does not even need to be there to write to both arrays).  Performance is impacted as the write will not be acknowledged until it has written to both arrays and it is not possible to confuiure Storage foundation mirroring to be asynchronous.

    If you want asynchronous writes, then you need to use a replication product on the array or the host.  The Veritas implemenation of this is Veritas Volume Replicator and this is an integral part of SF (you cannot use VVR without SF) and is present automatically and just requires a license to use.  VVR ris host-based replication over IP and sends the writes to the secondary host which writes to the array at the secondary site and VVR can be configured as synchronous or asynchronous.

    Mike

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  • mikebounds's avatar
    mikebounds
    Level 6
    11 years ago

    Storage foundation mirroring across sites works by have 2 (or more) SAN attached arrays and SF on the node that does the writes, writes to LUNs in both arrays synchronously (i.e the other node at the other site is NOT involved in the write and the node at the other site does not even need to be there to write to both arrays).  Performance is impacted as the write will not be acknowledged until it has written to both arrays and it is not possible to confuiure Storage foundation mirroring to be asynchronous.

    If you want asynchronous writes, then you need to use a replication product on the array or the host.  The Veritas implemenation of this is Veritas Volume Replicator and this is an integral part of SF (you cannot use VVR without SF) and is present automatically and just requires a license to use.  VVR ris host-based replication over IP and sends the writes to the secondary host which writes to the array at the secondary site and VVR can be configured as synchronous or asynchronous.

    Mike

  • Marianne's avatar
    Marianne
    Level 6
    11 years ago

    In addtion to Mike's excellent post - have you had a look at SFW Admin Guide?

    Extract:

    About mirroring
    A mirrored volume consists of at least two subdisks of identical size located on
    separate disks. Each time a file system or application writes to the volume, Veritas
    Storage Foundation for Windows transparently writes the same data to each of
    the volume’s subdisks.

     
    Add Mirror: The primary purpose of mirroring is to provide fault tolerance;
    however, mirrored volumes can also improve I/O performance for most
    I/O-intensive applications, which make substantially more read requests than
    writes. With mirrored volumes, write requests may take longer than with
    non-mirrored volumes, but the effects are typically minor.