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I wonder if someone can help me get educated about synchronous writes |
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to a file server over the network? Is this something that's designed |
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into specific apps or is this something that I have control of at the |
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sys admin level? |
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|
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I've recently built 2 TrueNAS file servers. The first (and main) unit |
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runs all the time and serves to backup my home user machines. |
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Generally speaking I (currently) put data onto it using rsync but it |
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also has an NFS mount that serves as a location for my Raspberry Pi to |
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store duplicate copies of astrophotography pictures live as they come |
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off the DSLR in the middle of the night. |
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|
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The second TrueNAS machine serves to back up this first machine but |
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resides at the other end of the house to protect data in case of fire. |
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Eventually I'll probably backup all of this offsite but for now it's |
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two old computers and a bunch of disks. |
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|
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The question about synchronous writes comes in the configuration of |
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TrueNAS. TrueNAS supports what it calls a ZIL (ZFS Intent Log) which |
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is a smaller SSD at the front end of the write data flow. The idea (as |
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I understand it) is that the ZIL allows writes to the server to be |
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cached quickly onto, in my case, an SSD, and then eventually written |
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to spinning drives when the system gets around to it. Once new data |
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arrives at the ZIL it remains until it's written and verified at which |
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time the entries in the ZIL are removed. The ZIL does not do anything |
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to speed up reads from the file server. |
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|
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The thing is that the ZIL is only used for synchronous writes and I |
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don't know whether anything I'm doing to back up my user machines, |
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which currently is just rsync commands, is synchronous or could be |
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made synchronous, and I do not know if the NFS writes from the R_Pi |
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are synchronous or could be made so. |
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|
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If someone can point me in the right direction in terms of reading and |
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study I'd appreciate it. |
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|
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Thanks, |
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Mark |