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  1. #1
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    Unanswered: Drives on Server and How to Define Raid for them

    Hello! I hope that I have posted in the right spot.
    We are looking for advise. I know that there is no right or wrong answer. "It depends."

    We currently have a server with the OS as Windows Server 2003 SP2 and SQL Server 2000 SP3. This Server has 6 physical drives; only 3 of these physical drives are being used. These 3 physical drives are 1 container with Raid 5. This 1 container is divided into 3 logical drives.

    We would like to fill the other 3 physical drive slots and create another container. We were thinking of making this Raid 1.

    I should put in my disclaimer that Raid 10 is out of the question and so is SAN.

    Is Raid 1 the best choice? This is my first question.

    Next is how should we split up the files among the containers.

    For example, OS, log and swap file on container 1 with Raid 1 and datafiles on container 2 with Raid 5?

    What are most people doing? Is there a standard? Can people provide examples of what they are doing or provide suggestions?

  2. #2
    Join Date
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    I might move tempdb container 1.

  3. #3
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    ILoveHorses,

    I would try and do the following if possible:
    - Move the OS to it's own HD
    - Keep the SQL data on the existing RAID5 drive
    - Put the SQL log files and OS Swap files on a RAID1 drive

    But, since I'm going to guess that rebuilding the box is out of the question(about what would be required to move the OS, I'm guessing), you can do the following:
    - Use 2 disks to create a RAID1 array. Move the SQL Log Files and the SQL TEMP database to this array
    - With the remaining disk the OS swap file here.


    If you were building from scratch I would recommend the following drive configuration:
    - OS drive: OS and Installed applications. OS Temp/Swap files (One Drive)
    - Data drive: SQL Datafiles (2 drives RAID1)
    - LOG drive: SQL Log files (2 drives RAID1)
    - TEMP drive: SQL TEMP Db (One Drive)

    In general I like to configure my systems like this. RAID levels and number of drives may vary with what I have available and my requirements.

    If you had a lot of data moving back and forth I would also recommend multiple drive controllers so that the Data drive(s) and the Log drive(s) would be separated to improve their speed.
    Life....Just another opportunity to live another day like a pirate....

  4. #4
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    I don't understand why you would consider RAID1 as an option but not RAID10. Can you explain what the issue is?

    Microsoft has some recommendations here:
    http://www.microsoft.com/technet/pro...ge-top-10.mspx

  5. #5
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    Agreed. I'm no hardware configuration expert but the answer to "Is Raid 1 the best choice?" is "it depends". Are you going for speed or resilience?

  6. #6
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    Quote Originally Posted by dportas
    I don't understand why you would consider RAID1 as an option but not RAID10. Can you explain what the issue is?
    RTFT (Read The Full Thread) ... the OP stated that RAID 10 was not an option in this case. Otherwise, I'm sure hubart would have added that to his recommendations.

    -- This is all just a Figment of my Imagination --

  7. #7
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    Quote Originally Posted by tomh53
    RTFT (Read The Full Thread) ... the OP stated that RAID 10 was not an option in this case. Otherwise, I'm sure hubart would have added that to his recommendations.
    I read it. That's why I asked the question.

    Obviously not a cost issue since RAID10 costs basically the same as RAID1 so if there is some technical reason for not striping then that may have a bearing on any other recommendations. That's why I wanted more information.

  8. #8
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    May 2004
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    Quote Originally Posted by dportas
    I don't understand why you would consider RAID1 as an option but not RAID10. Can you explain what the issue is?
    Well, lets start with the OP saying that he had 6 drive slots total and 3 available. Then, I'll add that to build a RAID10 array you need 4 drives minimum ( http://en.wikipedia.org/wiki/Nested_RAID_levels ). I'll finish with the assumption that I assumed in the post that they were not/could not re-build the server.

    Any RAID is preferable to the alternative of not RAID'ing drives for data security/protection or whatever you want to call it.

    In the end, when designing the HW for a SQL server you need to look at what the server is going to do, how fast it needs to do it, how much data is there going to be and most importantly.....how much money can you spend

    I don't have any issue with putting a RAID10 array in a SQL server under the right conditions. Just like I don't think that a RAID5 is a bad idea under the right conditions.
    Last edited by HubarttMeister; 01-29-08 at 10:12.
    Life....Just another opportunity to live another day like a pirate....

  9. #9
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    Quote Originally Posted by dportas
    Obviously not a cost issue since RAID10 costs basically the same as RAID1 so if there is some technical reason for not striping then that may have a bearing on any other recommendations. That's why I wanted more information.
    Huhhh ... try that one again. You are saying that a stripe of mirrors (or a mirror of stripes) cost about the same as a stripe?

    Wrong ... and thank you for playing. You more than double the cost, because if you have a stripe of 5 drives, and then mirror that stripe, you need 5 additiional drives plus supporting rackspace, electrical, etc.

    -- This is all just a Figment of my Imagination --

  10. #10
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  11. #11
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    Quote Originally Posted by tomh53
    Huhhh ... try that one again. You are saying that a stripe of mirrors (or a mirror of stripes) cost about the same as a stripe?
    Read the OP again. He said RAID1 - mirrored but no striping. As has already been pointed out though, I missed the point about the number of drivers.

  12. #12
    Join Date
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    If you have 3 unused drives, RAID 1 isn't an option either.

    RAID 1 is mirroring meaning you need a pair of drives, so 2, 4, 6, 8, etc.

    That said, if you have the drive space, I would choose RAID 1 above RAID 5 for speed any day. Sure modern day RAID 5 capable controllers hide its weakpoints by massive write cache but any seriously sized database soon outgrows that cache. The random read nature of database result in data often not being in cache, let alone any form of datamining that span multiple gigabytes of data which can't be held into cache.

    The question is if you can reinstall the machine from scratch using all 6 discs.
    I would take 2 discs and turn it into either a RAID 0 or RAID 1 config and partition it with a partition holding your OS and software and a partition for your tempdb, then take the other 4 discs and turn it into a second RAID 1 array and put your database on there.
    Most ideally you would put your log files on a separate array from your data files but its a choice between putting them on your first array with the tempdb (the OS should not have much IO though with windows you never know).

    It would be better however, log files are only written to while data is both read and write, keep that in mind when choosing your disc configuration that holds the log files, if space is limited placing data on RAID 5 and log on RAID 1 could really save your performance when volume processing is key as RAID 5 requires reads and transformations before data can be written, while RAID 1 is a simple identical write to two discs.

    Running the first array in RAID 0 does introduce a risk in guaranteeing uptime, but since neither your OS (which should be pretty stable after installation and can be ghosted) nor your tempdb (which is rebuild at restart anyways) requires mirroring, it saves some disc space. On the other hand, good RAID controllers can read from the two mirror asynchronously making reads potentially faster on RAID 1.
    Greetz,

    Bastiaan Olij

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