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  1. #1
    Join Date
    Dec 2005
    Posts
    22

    Unanswered: 2K and 4K page size

    ALL,

    I have two questions:

    1) What are the advantages and disadvantages using 4K or 8K over 2K apart from rowsize?.Is there any documentation on this?

    2) Are there any disadvantages in using file system for database devices over exteranal RAID devices?.

    Thanks in advance
    BSR.

  2. #2
    Join Date
    Dec 2005
    Posts
    22
    All,

    Can some one please respond to this?

    Thanks in advance
    BSR.

  3. #3
    Join Date
    May 2005
    Location
    South Africa
    Posts
    1,365
    Provided Answers: 1
    1) With a larger page size you can also have larger varchar columns

    With a larger page size more memory is allocated per read, and since more data (rows) is read into memory per page it can result in an increase in performance for e.g. reporting

    You might need more disk space. When a text or image column is initialised, a valid text pointer to the column is inserted into the table, and an entire data page is allocated to the column (2, 4, 8, or 16K depending on your logical page size).

    That means if you have a 1 GB table with a text or image data type on your 2K server, it will use 4 GB of space on a 8K server.

    Since more rows can fit onto a page it means that with allpage locking more rows are locked when the page is locked, decreasing concurrency. You might want to use row level locking if you don’t already.

    2) External RAID devices normally have a write cache with a battery backup that function independent of the OS. It can therefore outperform your local filesystem which has to wait for the write to complete (dsync/direct IO) to ensure integrity in case of OS/power failure.

  4. #4
    Join Date
    Dec 2005
    Posts
    22
    Thanks a lot PDreyer,

    What about performance of inserts and updates?.All our tables are allpages locking tables.

    Another question is Can I load the dump of 2k database on a 4k database?

    Thanks in advance
    BSR.

  5. #5
    Join Date
    May 2005
    Location
    South Africa
    Posts
    1,365
    Provided Answers: 1
    Quote Originally Posted by bsr
    What about performance of inserts and updates?.All our tables are allpages locking tables.
    Like I said before; Since more rows can fit onto a page it means that more rows are locked decreasing concurrency (preventing others from accessing previous available rows). You might want to switch to row level locking.
    Quote Originally Posted by bsr
    Another question is Can I load the dump of 2k database on a 4k database?
    No

  6. #6
    Join Date
    Dec 2005
    Posts
    22
    Thanks a lot Pdreyer.

    --BSR

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