Okay, so from reading another thread, my current understanding of the compression ratio shown in storage view, is basically summed up by this quote from danb35:
"A number of 1.09x means that you're storing 1.09x as much data as you're using drive space--you're using 1000 MB of pool space to store 1090 MB of data" - taken from this thread here: https://www.truenas.com/community/t...pression-ratio-numbers-in-freenas-mean.42330/
If this were a dataset, and NFS share we were talking about, the above would be pretty straight forward in my head.. I am using zvols and iSCSI shares unfortunately, and as such I am a little lost here. Follow me for a moment, and see if someone can explain this a little bit to me:
So hypothetically now, I grow my VM a ton, and now I'm sitting at 100GB of 100GB on my Windows partition, still with a 1.5x compression ratio, which leaves me a zvol that shows me 100GB used, and 1434GB free (approximately). Great. Subtract the 1400GB left from the pool, and the zvol should still have about 34GB available.. Windows doesn't see it that way, and am forced to extend C partition, but cannot as no more space is being presented.
How do I fix this so I can take advantage of the compression's space savings? Use thin provisioned ("sparse") zvols?
I'm not super big on that, but if it works it works.. My problem with that is, then those zvols would need to be overprovisioned technically. So if I wanted to actually use (80% of) my entire 1500GB pool's actual disk space, assuming a 1.5x compression ratio, I would need to provision a zvol that was (80% of) 2250 GB - if TrueNAS will even allow this! - EDIT: Seems it will using the force size flag, but still not sure its a good idea! Any advice appreciated!
"A number of 1.09x means that you're storing 1.09x as much data as you're using drive space--you're using 1000 MB of pool space to store 1090 MB of data" - taken from this thread here: https://www.truenas.com/community/t...pression-ratio-numbers-in-freenas-mean.42330/
If this were a dataset, and NFS share we were talking about, the above would be pretty straight forward in my head.. I am using zvols and iSCSI shares unfortunately, and as such I am a little lost here. Follow me for a moment, and see if someone can explain this a little bit to me:
- I have a pool with 1500GB available
- I create a zvol sized at 100GB (not thin provisioned)
- My pool now shows 1400GB available, 100GB used
- The zvol shows 100GB used 1500GB available (counts the available space on the pool too apparently)
- I create an iSCSI share, with a device-type extent mapped to the zvol I just created, and attached it to a Windows initiator
- From the Windows initiator, I copy a 20GB VHDX file to the drive, after formatting it in disk manager
- Windows shows I have 20GB used, and 80GB free on the partition
- TrueNAS shows the zvol has 100GB used still, but 1488GB available, and compression ratio 1.55.
So hypothetically now, I grow my VM a ton, and now I'm sitting at 100GB of 100GB on my Windows partition, still with a 1.5x compression ratio, which leaves me a zvol that shows me 100GB used, and 1434GB free (approximately). Great. Subtract the 1400GB left from the pool, and the zvol should still have about 34GB available.. Windows doesn't see it that way, and am forced to extend C partition, but cannot as no more space is being presented.
How do I fix this so I can take advantage of the compression's space savings? Use thin provisioned ("sparse") zvols?
I'm not super big on that, but if it works it works.. My problem with that is, then those zvols would need to be overprovisioned technically. So if I wanted to actually use (80% of) my entire 1500GB pool's actual disk space, assuming a 1.5x compression ratio, I would need to provision a zvol that was (80% of) 2250 GB - if TrueNAS will even allow this! - EDIT: Seems it will using the force size flag, but still not sure its a good idea! Any advice appreciated!
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