June 19, 20197 yr Hey, So a quick one hopefully, so recently added more disks to my library share, which are lower volume than original and current disks, i.e had 3x8tb and now added 4x4tb. Share is in high water allocation, I was wondering if running unbalance scatter job to rebalance data across the 7 drives would reset the high water "pass" count and instead of continuing on its current (2tb free atm) pass and retry from the start (i.e. 4tb free) given reduced disk space? I hope that makes sense?
June 19, 20197 yr Community Expert What do you have set as the Split Level? In any contention between Allocation and Split Level for choosing the target disk then Split Level always wins. The point at which Allocation method switches drives is always based on the largest drive. This gives split point of 8TB, 4TB, 2TB etc. On that basis the 4TB drives will not start getting used until the existing 8TB drives get to 2TB Free. Edited June 19, 20197 yr by itimpi
June 19, 20197 yr Author split set to any at the moment, not bothered about it, might end up setting 3 subdirs in future, but data no big enough to worry about it yet. drives I've moved 900gb to other disk but didn't seem to do much and continue filling up first disk rather than reset to 4tb free mark and fill disk 2 etc. I can't confirm but I believe its on the 2tb free pass atm so filling disk 1 until 2tb free mark and then moving down the drives but was hoping to move data around to force it down quicker instead of filling 75% of first disk before even touching empty 4tb drives Edited June 19, 20197 yr by Mizerka
June 19, 20197 yr Community Expert 7 minutes ago, Mizerka said: split set to any at the moment, not bothered about it, might end up setting 3 subdirs in future, but data no big enough to worry about it yet. drives I've moved 900gb to other disk but didn't seem to do much and continue filling up first disk rather than reset to 4tb free mark and fill disk 2 etc. I can't confirm but I believe its on the 2tb free pass atm so filling disk 1 until 2tb free mark and then moving down the drives but was hoping to move data around to force it down quicker instead of filling 75% of first disk before even touching empty 4tb drives Unfortunately not - that is the way High Water Allocation works. It works through drives in slot number order at each switch point. If you are really concerned then I think the only solution would be to have the 4TB disks on lower slot numbers than the 8TB ones so they started being used first when the 4TB point was reached. Since you only have single parity this could be done without recalculating parity if you really wanted to do this. However is it worth it?
June 19, 20197 yr Author 39 minutes ago, itimpi said: Unfortunately not - that is the way High Water Allocation works. It works through drives in slot number order at each switch point. If you are really concerned then I think the only solution would be to have the 4TB disks on lower slot numbers than the 8TB ones so they started being used first when the 4TB point was reached. Since you only have single parity this could be done without recalculating parity if you really wanted to do this. However is it worth it? I see, well thanks for clarifying. Is there a recommended drive allocation when using high water? Also from what you're saying, the high mark threshold/pass is set when it has reached a breakpoint on a single disk? so in theory if I were to put empty drives ahead of 8tb (filled one) when 8tb reaches 2tb high mark, it'd run through disks in order and determine new mark? And as you said, its not a huge deal, I'll be upgrading the wd1tb's to 10tb tonight so might move the drives around. So I'll break parity and move it down to data and create a new 10tb parity and 2nd will just go into data. Planning on grabbing a 2nd shelf at some point, but until then will probably rock single parity, given sas shares are sitting empty whilst I prep vmware move.
June 19, 20197 yr Author flooded the library a bit to see what happens, and look like it was on the 2tb pass, filled disk1 until 2tb, and now going for disk 2. With that in mind, I suppose ideally you would keep smaller disks as lower count if you care for "higher use" of high water allocation, as in my case, you won't even touch 4tb drives until you have 18tb's writted to share. I'll expand with 10tb's and re arrange to see what happens, I would expect it to continue filling disk 2 until 2tb free and then look at disks again to choose best target.
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