This may seem like a silly question due to its obvious nature, but am I correct in saying that since the cache drive is outside the array, it is unprotected and if it crashes or becomes corrupt, you will lose whatever is on it.

 

So for example, if I am copying a lot of data to my array and that data lands on the cache drive first and then at some point before the mover starts, something bad happens to that drive, that data could potentially be lost?

 

Of course this isn't necessarily a 'data loss' scenario because I should still have the data in its original source location, just wanted to bring this up.

 

I suppose the only way to protect against this might be to have a cache pool? Does that offer protection?

Juat to add to this. How often does the transfer from cache to disk occur.

You can actually schedule the mover under settings/scheduler, as often as you like.

And am I right in saying that when u copy a file to the server it goes into the cache and then transfers over

To answer Ashmans question.

 

Yes, it's outside the array (sort of...*) it's not protected by your parity and if it crashes or becomes corrupt you will potentially lose the data on it.

 

The trade off with cache enabled shares is that you speed up writing to the cache, but that data isn't immediately parity protected. (You can also have non-cache shares that do not ever touch the cache and go directly to the array)

 

A cache pool can be configured in a lot of different ways, the most common configuration is as a Raid 1 pool. Meaning that every byte of data is mirrored onto another disk. If one disk fails the data exists on that other disk. Some people use the pool option to "build" a bigger cache drive with Raid 0 (which is more like JBOD, and has no redundancy)

 

* I say sort of because it's totally not parity protected, but when you have a cache disk you have /mnt/user/ and /mnt/user0/ user0 is all of your disks minus your cache disks. So you can kind of call it like it were part of the user shares on your array even though it's not.

 

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Yes when data is waiting on the cache to be moved by mover it's not parity protected.

Cache Pools were introduced to add redundancy to the cache.