SQL Server Performance

disk transfer rate

Discussion in 'Performance Tuning for DBAs' started by yxl1108, Nov 25, 2002.

  1. yxl1108 New Member

    My server, according to the specification, can have 160MB/sec disk transfer rate. But I did some experiment in SQL Server, by executing query like "select count(*) from table_name" with a cool buffer, I can only have around 108MB/sec. I am wondering what's wrong.
  2. joechang New Member

    nothing is wrong,
    the 160MB/sec quoted on your system is actually the scsi bus bandwidth,
    the bandwidth capability of each individual disk is less
    the current generation of disk drives might be in the 50-60MB/sec range,
    the previous generation was in the 30-40MB/sec range
    hence you probably have 3-4 disk drives striped together

    it is not likely that you will be able to fully saturate the scsi bus,
    hence if you need greater disk bandwidth, you will need multiple scsi channels

    for that matter, to get better than 100MB/sec, you should be on a 64-bit PCI bus, 66MHz or PCI-X is preferred
    2-4 scsi channels per adapter is ok,
    it is also ok if the cumulative scsi bandwidth is somewhat
    greater than the pci bus bandwidth
  3. satya Moderator

    Getting 75% of the bandwidth on disk transfer rate, the rest needed by the OS.

    Satya SKJ

Share This Page