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Conference cookie::raid_software_for_openvms

Title:RAID Software for OpenVMS
Notice:READ IMPORTANT NOTE IN 3.15, V2.4 SSB Kit in 3.176
Moderator:COOKIE::FROEHLIN
Created:Fri Dec 03 1993
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:341
Total number of notes:1378

340.0. "Destroy the RAID?" by VAXRIO::TULA () Fri May 30 1997 12:49

    Hi,
    We have a raid 0-1 of ten disks configured in a client.  This raid is
    supposed to be used by a pooling software(not a Digital software).  The
    company responsable for this software said that they use a lot of
    directories and that they write and delete a lot of files in that
    directory.  As used today it will be like the above:
    DKB300:[DIR1]
    DKB300:[DIR2]
    DKB300:[DIRn]
    They said that the perfomance of this configuration will be better if
    they don't use the stripe and live the disk separate like bellow:
    DKB300:[DIR1]
    DKB400:[DIR2]
    Is that right, am i suppose to destroy the raid-set?
    Thank you in advanced,
    Tula   
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340.1COOKIE::FROEHLINVMS...riding into the setting sun!Fri May 30 1997 13:4218
  <<< COOKIE::DISK$SYSTEM_3:[NOTES$LIBRARY]RAID_SOFTWARE_FOR_OPENVMS.NOTE;1 >>>
    Tula,
    
    forgive me but I have no clue what you are talking about.
    
>    We have a raid 0-1 of ten disks configured in a client.  This raid is
    
    Ok, a ten member RAID 0+1 set. Using RAID Software?
    
>    supposed to be used by a pooling software(not a Digital software).  The
    
    Pooling what? What is this software doing?
    
    All the rest I have no idea what this is all about. Could you please
    explain in more details?
    
    Thanks
    Guenther
340.2Trying to clarifyVAXRIO::TULAMon Jun 02 1997 10:2814
    - We have a HSZ40 controller and the disk are in a storage works.
    - The software that i have mentioned is not from Digital, i have only
    mentioned it trying to make the note more clear, i'm sorry about it.
    - What i'm trying to discover is:
    	What is the best solution when you have many directories with many
    files frequently deleted:
    Using a stripe set (which make your system more manageable since you
    will see only one disk) 
    or leaving the disks without a raid solution and putting each directory
    in a disk.
    It will be good if i can have an answer in terms of performance.
    Thank you in advanced,
    Tula
    files frequently deleted, what is the best  
340.3COOKIE::FROEHLINVMS...riding into the setting sun!Mon Jun 02 1997 13:3552
    Tula,
    
>    - We have a HSZ40 controller and the disk are in a storage works.
    
    I assume you they plan to use RAID in the HSZ40 controller, right?
    
>    - The software that i have mentioned is not from Digital, i have only
>    mentioned it trying to make the note more clear, i'm sorry about it.
    
    Why is this software deleting so many files? Are they by chance trying
    to get a "cheap" database my abusing the files system?
    
>    - What i'm trying to discover is:
>    	What is the best solution when you have many directories with many
>    files frequently deleted:
    
    Deleting files frequently is always a time consuming operation on
    any/most file systems. I/Os by the files system are mostly small in
    nature (1-2 kB) and mostly serialized for synchronization. Therefore
    disk striping will not help improving performance in this area.
    
>    Using a stripe set (which make your system more manageable since you
>    will see only one disk) 
    
    In case the application needs a large disk volume and the only other
    option would be a VMS bound volume set then I'd recommend a controller
    based stripe set for better load balancing. In case of striping it is
    always adviced to add shadowing for acceptable availability of the
    stripe set.
    
>    or leaving the disks without a raid solution and putting each directory
>    in a disk.
    
    It's cheaper and should not be slower than striping when it comes to
    file deletions.
    
>    files frequently deleted, what is the best  
    
    Don't do it!!! Use a database product instead and store the data there.
    Or keep the files and just reuse them with a small database which maps
    between the permanent file names and the files' contents.
    
    If the design has been completed, as I assume, and they have to 'live'
    with the many file deletions I'd recommend to use a solid state disks.
    
    Or maybe a closer look on what the application is doing right now and
    slightly tweak it a bit.
    
    For more discussions on file deletion look at many many entries in 
    VMSZOO::RMS_OPENVMS. Especially directory file size above 128 blocks.
    
    Guenther