April 25, 201610 yr I have two 3TB drives in my array for data. I have all shares set to use both drives, however the first one is at 70% total usage and the second one is at 50% usage. I keep getting high usage alerts < 70% for the first drive. Is this normal?
April 25, 201610 yr Author Maybe? It depends on what your split level and allocation methods are set to be. They are set to default. I didn't make any changes to those. All set to High-Water/Automatically Split any directory as required.
April 25, 201610 yr Community Expert Maybe? It depends on what your split level and allocation methods are set to be. They are set to default. I didn't make any changes to those. All set to High-Water/Automatically Split any directory as required. In which case there does not seem to be a problem! With High Water then the first disk is used until it reaches 50%, and then the second disk is used until it reaches 50%. unRAID then switches back to the first disk until it reaches 75% (half of remaining space) and then switches back to the second. The points at which the switch happens are easy to work out if all drives are the same size. With mixed disk sizes then it gets more complicated - you really need to read the wiki article on Split Levels carefully to understand when the switch points occur. If you want them to be used more evenly then "Most Free" might be the way to go?
April 25, 201610 yr Author Maybe? It depends on what your split level and allocation methods are set to be. They are set to default. I didn't make any changes to those. All set to High-Water/Automatically Split any directory as required. In which case there does not seem to be a problem! With High Water then the first disk is used until it reaches 50%, and then the second disk is used until it reaches 50%. unRAID then switches back to the first disk until it reaches 75% (half of remaining space) and then switches back to the second. The points at which the switch happens are easy to work out if all drives are the same size. With mixed disk sizes then it gets more complicated - you really need to read the wiki article on Split Levels carefully to understand when the switch points occur. Okay great thank you!
April 25, 201610 yr Something to take note of: even though it might seem like a good idea to use most free, it might not be with spindle drives i.e. all normal HDD. Assuming that you will utilise the reconstruct-write (aka Turbo Write) method to speed up write speed, Most Free theoretically would lead to slower speed on average. Reason is that the drives will have to be switched between read and write relatively a lot more frequently which adds latency to the write process. There's a reason High Water is the default mode. Personally I think Most Free is more relevant if your array is made up of SSD - which would benefit from having evenly distributed free space (which is a form of over-provisioning which helps improve performance).
April 25, 201610 yr Personally I think Most Free is more relevant if your array is made up of SSD - which would benefit from having evenly distributed free space (which is a form of over-provisioning which helps improve performance). All of my shares on both my servers are set to most free. My reasoning is that Should I ever have more drives drop dead than my parity system allows (either 1 or 2 drives), then I am lessening the amount of files that I will lose. IE: If I have 2 drives drop dead on a single parity unRaid, then I'd personally rather only lose say 20% of the irreplaceable family pictures than 100% of them. I'm just minimizing the loss of files in case of a disaster... The reverse is also true however. Should I have all the pictures stored on a single drive, the odds are decent that I wouldn't have lost anything, but I'm running the risk of losing everything. To me and my usage case, I'd rather lose some then ever take the chance that I would lose all. And additionally, most-free also will help with the number of streams you're able to handle concurrently, because your most recent movies will be almost guaranteed to be stored on different drives instead of all the same drive (which will thrash extensively trying to read 5-10 streams at the same time) And, yes itimpi/garycase before you mention it, I do realize that unRaid is not a backup, and I do have backups of the outright very important stuff
April 25, 201610 yr Personally I think Most Free is more relevant if your array is made up of SSD - which would benefit from having evenly distributed free space (which is a form of over-provisioning which helps improve performance). Just want to mention that an array of SSDs is not recommended or supported. Trim operations have a tendency to invalidate parity (or so I've heard)
April 25, 201610 yr Just want to mention that an array of SSDs is not recommended or supported. Trim operations have a tendency to invalidate parity (or so I've heard) I subscribe to Linus' law: if thou can use something in a certain way, just do it and disregard whatever it was intended to be used for.
April 26, 201610 yr Thanks for your replies, I assume I need to enable the AFP tab under settings network services if I want to write to the server from the mac, is there anything I need to be mindful of doing that? Peter
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