Results 1 to 6 of 6

Thread: DLT Drives

  1. #1
    3 Star Lounger
    Join Date
    Apr 2002
    Location
    UK
    Posts
    298
    Thanks
    6
    Thanked 0 Times in 0 Posts

    DLT Drives

    Hi,

    I have a Compaq DLT 7000 running on an Adaptec 2940UW SCSI card at interupt 6 (two 36Gb drives on 0 & 1) which I am using to backup a local system Win2K soft RAID array (stripe) but I am getting only 200Mb a minute out of it meaning my 120Gb backup will take around 10 hours. I'm sure the device can backup at near 2

  2. #2
    Plutonium Lounger Leif's Avatar
    Join Date
    Dec 2000
    Location
    U.K.
    Posts
    14,010
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: DLT Drives

    Are you using any compression? If you are and (e.g.) the compression rate is 2.5:1 you could well be getting 500Mb a minute in 'real' terms.
    It might be worth doing a test run of a - say - a 1Gb set and timing it.

  3. #3
    Plutonium Lounger
    Join Date
    Nov 2001
    Posts
    10,550
    Thanks
    0
    Thanked 7 Times in 7 Posts

    Re: DLT Drives

    These devices typically run in one of two modes, Start-Stop and Streaming.

    If your backup softrware doesn't provide the data to the device fast enough for it to stream then it will stop, back up a bit, and start again. This can potentially cause it to run as slowly as 10% of its maximum speed. Typical causes of this are a system that is out of CPU power, or a badly fragmented disk.

    You may be able to get an improvement by defragmenting your hard drive, other than that it typically takes a faster CPU <img src=/S/exclamation.gif border=0 alt=exclamation width=15 height=15>

    StuartR

  4. #4
    Platinum Lounger
    Join Date
    Jan 2001
    Location
    Quedgeley, Gloucester, England
    Posts
    5,333
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: DLT Drives

    The usual motto with backup devices (and anything in computing in general) is that "it always taken longer than you think". To back up Stuart's suggestions I would add that I would put my ear close to the DLT to see if it's streaming or not. We usually reckon on a 2x compression ratio for disk to tape, and Leif's point is well made.

    John
    <font face="Script MT Bold"><font color=blue><big><big>John</big></big></font color=blue></font face=script>

    Ita, esto, quidcumque...

  5. #5
    3 Star Lounger
    Join Date
    Apr 2002
    Location
    UK
    Posts
    298
    Thanks
    6
    Thanked 0 Times in 0 Posts

    Re: DLT Drives

    Hi Guys,

    Thanks for those responses ... yes the device goes, then stops, then seems (I guess) to back up some, then carry on. The system it is on it a dual PIII/500 (ordinary, not Xeon) but will soon be replaced by a P4/1.7 so perhaps that will improve performance.

    Thanks again

  6. #6
    5 Star Lounger
    Join Date
    Jan 2001
    Location
    Cairns, Queensland, Australia
    Posts
    885
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: DLT Drives

    The other factor to bear in mind is Exchange. If you happen to be backing an Exchange server the backup software must authenticate to open each mailbox before it can access the contents.
    Granville

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •