Separation of MDF and LDF files in a VM enviornment

  • SQL_Padre

    Right there with Babe

    Points: 768

    Within a VM environment that is using one massive array of hard disks. is it really beneficial to create 2 VM Drives out of the same array to separate your MDF and LDF files?

    it would seem if I am carving out 2 drives from the same array of disks, it sort of defeats the purpose of separation. the array will still have to do sequential and random read/writes on the same physical disk, i.e. no performance gain.

    or am I totally missing the concept of VM Environments and how carving out disk drives work?

    SQL Padre
    aka Robert M Bishop

    "Do or do not, there is no try" -- Yoda

  • alanspeckman

    Hall of Fame

    Points: 3344

    In my experience, they would have to be on seperate LUNs, not the same LUN carved out into 2 drives. I'm somewhat SAN-challenged in my terminology, but I think that is correct.

  • Bill Talada


    Points: 11956

    I've used the rule in the past of logs get mirrored and data gets RAID 5. It seems to be a losing battle against the network guys who like to buy TB size drives and treat sqlserver as if it worked like file systems. I ask for many separate medium size physical drives and they usually just stick database files on the NAS.

    At a minimum separating clustered/heap data from nonclustered indexes, log, and tempdb will give pretty good performance. We spend time optimizing only to have the disk access get single-threaded in the end by lack of understanding with network guys.

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