i just noticed several mentions in the forums of something called a cache disk.  i found a very small paragraph about it in the wiki but i am wondering if someone can point me to more details on it.  how do i set it up?  what are the requirements?  and so on.

 

You will need the "PRO" version of unRAID.

Then you need a spare disk on one of your controllers.

Stop the array.

Go to the Devices screen.

scroll down to cache device: and select a the SPARE drive.

Go back to the main page and enable the array.

 

Now when you write to a user share on the array, it will be written to the cache disk at a higher rate then the protected array.

Overnight a job will run called mover which moves data from the unprotected cache disk to the protected array.

sweet! thanks!

is this disk like the parity disk where it has to be at least as large as the largest disk in the array or can it be any size?

It can be any size.  If it is not big enough for the file being copied to the server it will not be used and the file will be written directly to the data disk.  In the same way, if it is full and does not have enough space for the file being copied, it will not be used.

 

For that reason, it should be big enough to hold the amount of files you would typically write in a single day, since the files are moved from it to the parity protected array in the middle of the night.

 

Joe L.

awesome - thanks!

The cache drive makes a big difference.  My writes jumped from ~14 MB/s average to ~35 MB/s average.

 

While we're on the subject, can someone give me a link to the part of the manual/wiki that describes how to change the scheduled move time?  I was looking for it the other day and couldn't find it anywhere.  Thanks.

While we're on the subject, can someone give me a link to the part of the manual/wiki that describes how to change the scheduled move time?  I was looking for it the other day and couldn't find it anywhere.  Thanks.

 

That's a good question, and I'd like to add it to the FAQ, if someone will describe the procedure for adjusting the time, or point to where this has been answered previously.

 

By the way, I owe you an apology, for never getting back to your earlier questions.  I've been feeling somewhat overwhelmed, and a little burnt-out.  If you don't mind restating what you wanted, I'll try to get back to it.

Look into the "cron" / "crontab" commands for scheduling. ( random google reference link: http://www.thegeekstuff.com/2009/06/15-practical-crontab-examples/ )

Here's the relevant bit from http://lime-technology.com/forum/index.php?topic=1731.0:

 

* The format of the "Mover schedule" string follows the linux "crontab" format.  In a future unRAID OS release, we plan on making this more user friendly, but here is the description of this format:

 

The crontab format consists of 5 fields separated by spaces.  Individual fields may contain a time, a time range, a time range with a skip factor, a symbolic range for the day of week and month in year, and additional subranges delimited with commas. If you specify both a day in the month and a day of week, the result is effectively OR'ed: the crontab entry will be run on the specified day of week and on the specified day in the month.  A field consisting of an asterisk ('*') indicates "every" time of that field.

 

  Examples:

 

  # MIN HOUR DAY MONTH DAYOFWEEK

  # at 3:40 a.m. every day

  40 3 * * *

 

  # every two hours at the top of the hour

  0 */2 * * *

 

  # every two hours from 11p.m. to 7a.m., and at 8a.m.

  0 23-7/2,8 * * *

 

  # at 11:00 a.m. on the 4th and on every mon, tue, wed

  0 11 4 * mon-wed

 

  # 4:00 a.m. on january 1st

  0 4 1 jan *

Thanks sonofdbn, that's exactly what I was looking for.

 

By the way, I owe you an apology, for never getting back to your earlier questions.  I've been feeling somewhat overwhelmed, and a little burnt-out.  If you don't mind restating what you wanted, I'll try to get back to it.

 

Was this directed at me?  If so, no worries, because I don't remember what I asked you!