An issue with balancing from an SSD

[hsehestedt]

I have an issue with balancing from an SSD for which I first need to explain my configuration.

The notes for the SSD optimizer stated that if you are performing duplication, you would need to have multiple SSDs. I understand why this would be the case. I had inquired here on the forum whether I could simply partition my SSD into multiple partitions to satisfy this need but found that this is not the case. It was suggested that I could create 2 levels of pools to work around this. As a result, this is how I ended up configuring my system:

I have one drive pool that has the drive letter Y: which consists of five 8TB disks. Several of my folders are configured with a 3x duplication.

I then have a second pool that consists of my SSD and drive Y:. This pool has the drive letter Z:.

I have my balancing rules set to rebalance immediately (for now, for testing).

As a test, I drop a good-sized stack of files onto the SSD. This works great. The files get moved off of the SSD to my Y: drive where the 3x duplication is correctly applied.

However, here is my problem: One of these folders contains many small files that contain important information that I want duplicated. Because I am using this dual tier of pools, my first pool that contains the SSD and the other pool has no duplication configured. The duplication happens at the second level. As a result, it only moves files off of the SSD when the balancing rule thresholds have been met. The minimum amount of changed data that can be set for the threshold seems to be 1GB. However, as I noted, the one folder has many very small files. As a result, this trigger of 1GB is not reached leaving these files stuck on the SSD and thus not duplicated.

My question: Is this simply a limitation of my configuration or is there some way that I can force the data to be moved off of the SSD without having to wait for a 1GB threshold to be reached?

[Shane]

If the balance ratio slider for the Z: pool is set to 100% it should be balancing upon any discrepancy; if that is so set but not doing so, try un-ticking the "Or if at least this much data needs to be moved" box?

[hsehestedt]

Unfortunately, I had tried this, but it did not work. I don't know what criteria it uses to determine that the balance is not 100%. Let's say that it looks at tenths of a percentage. The problem is that my files are so small, that it sees the balance as still being 100%.

I feel like a little explanation is in order here. My tool pool is rather large, I believe it is currently on the order of 36TB. I use that size because I do in fact have a lot of very large files. However, I do a lot of work with very small batch files and documents. Some of these can very small, on the order of a few KB, but nonetheless they are the result of a lot of intensive research and testing, so I want these files on the array, and I want them protected. Likewise, I generate a lot of documentation in Word. These documents start life as a group of individual small docs that will eventually be combined into a larger document. But even an 80-page document many only be a couple of MB. However, in the meantime, they are very small.

Let's make the assumption that the balancing sees an out of balance condition at 99.9% (this is just a guess on my part). That would mean that 0.1% would still be equivalent to 3.6GB that would have to change. At that point I could manually set the threshold to 1GB instead, but you can fit a whole lot of Word docs and batch files into 1GB.

I should note at this point that I have raised this issue with support, and they are kindly looking into the matter with development. But I sincerely appreciate your response.