Ian, there are two parts in that nice Howto that I would amend, especially for people new to this stuff, who will tend to follow it blindly (as I did for other parts :-).
The first issue is your config file example with a copy of the 'content' file on each and every disk.
You do mention that this is overkill, but a negligible cost.
On my own system, the content file is over 360MB in size. While it's true that is not much compared to a 2TB drive, it's still 360MB :-)
I think you should not recommend placing one on the parity
drive, for the following reasons :
- many users have data drives with the same size as the parity drive
- many will not use your 'unprotected' scheme and run snapraid on the entire data disks
- we know that the parity file is always a bit larger than the largest occupied space on a data disk
(depending on the number of files, their size, the block_size setting etc.)
- thus a sync with an almost-full data disk as large as the parity disk may fail, as the parity file runs out of space
(we see a lot of new users scratching their heads at this on the snapraid forum...)
So, placing an additional content file on the parity disk only compounds the problem.
Whereas, having one on each data disk, but not the parity disk, would give the parity file a head start of twice the content file's size (as it is excluded from sync).
In my case, 720MB might conceivably make the difference between a failed and a successful sync, if one of my data disks were nearly full.
The second issue is in the 'cron' section at the end, in which you "don't recommend to sync more frequently than hourly"...
If some users who are not familiar with the concepts involved interpret this as a go-ahead for the hourly cron, they are bound to get into trouble because sync will repeatedly run while they are using the system and writing to the data disks...
I would turn it around and expound on the "fairly static data" notion, insisting that a nightly sync should be enough in most cases, and needs to happen when the system is idle...
Just my 2 cents of course, but a few years in Help Desk tend to make one cautious :-)