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Forums : Technical Support : how to determine resrources virtualbox/cosmo are being used
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David

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Message 21348 - Posted: 28 Apr 2017, 23:04:03 UTC

1. Since boinc/cosmo are running in a virtualbox, how can I tell where everything is physically?

I ask because I have an nvme drive as boot/sda but I don't want it thrashing all the time so i want the workfiles for cosmo to reside somewhere on sdb, if the disks are hit frequently. These nvme drives are NOT cheap and will wear out so if the drive is heavily used, I want it to use the sbb, which is a mechanical SATA drive. Of course, if it is all happening in RAM (32 Gb) then the point is moot, unless the saves that happen every so often make heavy use of the main drive. So, how do I determine which is happening, and if needed, how to force the data files to reside on sdb?

Thanks.
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Misho

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Message 21349 - Posted: 29 Apr 2017, 3:45:12 UTC

Hello David.
I am not sure that my answer is right but i think it is.
I have 32GB ram too and have RAMdisk (4GB) where i install BOINC manager AND VirtualBox software. When i check the task of C@H in virtualbox the virtual machines are stored in this RAMdisk and i think nothing is in my HDD. But i am not sure that this is 100% right.
I hope that someone from C@H will answer better than me.
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Jim1348

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Message 21351 - Posted: 29 Apr 2017, 14:04:11 UTC - in response to Message 21348.  

I would just use a write-cache, which directs all writes to the RAM memory until it is flushed to the SSD, thereby saving the SSD from most of the writes. Though if you have a crash, then you lose the unwritten data, but that is no big deal for me, since I use dedicated machines that seldom crash, and I have a backup power supply (UPS) to guard against power losses.

This is what I use on Ubuntu 16.10 for using half (16 GB) of my 32 GB main memory for a cache, and setting a two-hour time between cache flushes:

Set write cache to 16 GB: for 32GB main memory:
sudo sysctl vm.dirty_background_bytes=16000000000
sudo sysctl vm.dirty_writeback_centisecs=1000 (checks the cache every 10 seconds)
sudo sysctl vm.dirty_expire_centisecs=720000 (pages older than 2 hours are flushed)

Also, I turn off swap, since it is not normally needed with that much memory anyway:
sudo sysctl vm.swappiness=0

And it appears that Linux is smart enough to reduce the cache as necessary if you need more than 16 GB for working memory. I have not had a problem with it thus far.
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Message 21355 - Posted: 30 Apr 2017, 12:31:43 UTC - in response to Message 21349.  
Last modified: 30 Apr 2017, 12:33:01 UTC

Hello David.
I am not sure that my answer is right but i think it is.
I have 32GB ram too and have RAMdisk (4GB) where i install BOINC manager AND VirtualBox software. When i check the task of C@H in virtualbox the virtual machines are stored in this RAMdisk and i think nothing is in my HDD. But i am not sure that this is 100% right.
I hope that someone from C@H will answer better than me.


That's correct, currently no disk writes are performed from inside the VM except for the result files, as everything is inside a RAMdisk. However, at some point this will likely change as it can make the RAM requirement quite high for Docker images that are pretty big.
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David

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Message 21396 - Posted: 4 May 2017, 4:43:52 UTC

'Twould be nice if I could see that graphically. There are tons of things we Linux/UNIX folks could handle better if we could see each section graphically. I personally don't have the talent for writing those.
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Forums : Technical Support : how to determine resrources virtualbox/cosmo are being used