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I have two hard disks in my server. One of them is 300 GB and very silent. The other one is 750 GB and makes some noise (it's working perfectly, it's just not a silent drive). Both are connected through SATA2.

My idea is that the silent drive should handle things which happen more frequently. And let the larger HDD sleep for most of the time. I would get something like this: (More services will be active in the real scenario)

Active, silent and smaller:

  • Web site.
  • Asterisk server for VOIP (SIP) routing.

Sleepy, loud and larger:

  • FTP server.
  • Mercurial server.
  • Backups

My questions:

  1. Does it sounds like a good plan? Why? Why not?
  2. How do I set the time it should take before a HDD goes to sleep? What times do you think would be suitable?
  3. Should I let my active HDD go to sleep as well after a certain interval?
  4. Is it possible to monitor when and which application (process) accesses a HDD? It would be a great help in making sure that applications which shouldn't access the passive HDD does anyway. And also to set the sleep timeout I guess.
  5. Does the kernel access HDD's periodically or something else I should watch out for as it would take my HDD out of sleep mode and spin up without a good reason to?
  6. Anything else I should think about when I setup this server?
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2 Answers 2

You can use the hdparm command to shutdown the HD after some ide time.

Example : hdparm -S 244 /dev/sda will set the idle time before shutdown to 2 hours.

I'm using this for a file server that has some disks that are not used very often but you need to keep in mind that each time you try to access a "sleeping" HD it will take a few seconds to have it back "online".

To monitor what a process is doing use strace.

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lsfs can also be used to see which files are currently being opened on different devices. –  Joseph Kern Aug 11 '09 at 14:07

I'd be surprised if you could get this to work consistently - although it's a great idea - I'm just pretty sure that some bit of code or another would wake up the second disk every so often and put paid to your plan.

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