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Linux Help with RAID 5 on Xubuntu file server

Discussion in 'Software' started by WhiskeyAlpha, 28 Aug 2008.

  1. WhiskeyAlpha

    WhiskeyAlpha New Member

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    Hi,

    After following Glider's rather excellent server guides last year (and continually asking him questions ever since ;)) I have a very solid and nippy little fileserver.

    The touble lies in the word, "little". I only have an 80GB drive in there (it was initially just 'an experiment' you see) and desperately need more space.

    The old mobo in there has 3 spare SATA ports, so I was considering adding an additional 3 x 500GiB drives in software RAID 5 (whilst leaving the boot drive as it is). As I understand it, that will give me 1TB of 'useable' storage on the 3 drives (with 500GB reserved for parity).

    I found this guide which makes it all look fairly straight forward and I'm sure I'll be able to follow it.

    However, I do have some questions (some may make you laugh) about the procedure and software RAID in general:

    1. How would I know if a drive had failed (and hence needed replacing & rebuilding) in a headless fileserver?
    2. How would I identify which drive physically needed replacing when a problem occured?
    3. Is a 3.06Ghz pentium 3 with 1GB of RAM gonna hack it?
     
  2. cyrilthefish

    cyrilthefish New Member

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    1 and 2 i can't help with, but for #3, i've run software raid 5 of a gen 1 mini-itx board before (800mhz via CPU with 512mb PC133 ram, somewhat less performance than a 500mhz pentium3) with no noticeable reduction on speed.

    Was limited to a 100meg LAN though, i'm guessing gigabit will be more demanding, but for 100meg you have no worries at all.

    never saw my main PC go much above 5% cpu usage with a cheapish mostly-software raid5 card either... max 5% cpu usage under extreme HDD testing on a 6000+ X2 CPU...
    I feel the CPU-hit of software/part-software raid is massively overblown...
     
  3. WhiskeyAlpha

    WhiskeyAlpha New Member

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    Thanks, I agree to be honest.

    I think particularly for a (domestic) file server, it can spare the necessary clock cycles for the parity calcs.

    Unfortunately, it's the first 2 points that are making me hesitant to proceed.
     
  4. Fophillips

    Fophillips New Member

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    You would either need to login remotely at regular intervals, get a status report sent to you (internal email?), or have a web-based health monitor (webmin?).
    Any of the above.
    More than enough power.
     
  5. cyrilthefish

    cyrilthefish New Member

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    Must admit i've not had any experience with drives failing in raid arrays... but it generally is fairly obvious when a drive fails badly due to the noise :p...

    If you don't get horribly grinding noises/whatever from a drive if a drive in the array fails, you could boot an OS off a CD and do a quick test of each HDD manually one at a time...
    It'd take time, but still should be fairly quick to spot a suspect drive
     
  6. Elv13

    Elv13 New Member

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    One of those (and much more possibility):
    -Foward/alias your local mail (every accoutn normally have a mail box on linux, for cron stuff mainly) to a "real" mail box, or setup the internal one to availible outside of localhost.
    -Do a cron job to check the state and send an email
    -Put a 5$ LCD/LED display on the serial port of your file server to display drive health.
    -Use monitoring software
    -Find a circuit with a serial port and a transistor to light a LED for each drive using USBserial/COM1/LPT1. do something like
    while [ `<comamnd to check drive> | grep State | grep -o "running"` ]; do echo 111111111111111111111111111111111111111 > /dev/ttyS0; done
    to trigger the transistor, but it will eat a lot of cpu, so it is a bad idea, but a State LED is cool. You can also une a PIC chips to do it, but now it will be much harder. You can also use a buzzer (irriting sound things) instead of a LED if you dont see the file server. The command is mdadm if my memory is good, but i never used it.
     
  7. Fophillips

    Fophillips New Member

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    Not if you do:
    Code:
    while [ '<command to check drive> | grep "State.* running"' ]; do
      echo 111111111111111111111111111111111111111 > /dev/ttyS0
      sleep 1
    done
    
     
  8. Elv13

    Elv13 New Member

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    but then it will trigger off during 1 second, it need continuous input if it don't use some kind of microprosessor (PIC).
     
  9. Fophillips

    Fophillips New Member

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    Ah, good point.
     
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