ZFS, OpenIndiana and 4K Issue: Seagate Barracuda Green 2TB

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abrookewood

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Mar 20, 2012
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I am in the process of moving my current ZFS Pool from Solaris Express 11 to OpenIndiana and planned to buy one or two 2TB drives as part of the migration. I currently have the WD 2TB Green drives which are definitely affected by the 4k issue (they show an offset of 9) and figured I would assess different drives to see if I can get around this (rather than doing the whole BSD + GEOM thing).

Has anyone used these drives in a ZFS system and if so, do they automatically align correctly or did you have to do it manually?
Seagate Barracuda Green SATA 6Gb/s 2TB Hard Drive .

The reason I ask is that they include "Seagate SmartAlign™ technology" which is supposed to solve this at the firmware level, but which isn't really described.
 
Anyone? For what it is worth, I went ahead and ordered the drives so I will let you know how they go.
 
Personally I would just go ahead and manually 4K align them, especially if you are mixing Seagates and WD's. Even if the SmartAlign thing works great, the WD's don't have it anyway. From what little I've read about SmartAlign it tries to do some kind of caching or reordering to try to hide the performance hit from misaligned sector writes. I don't know much about that specific technology, but it sounds like the kind of thing ZFS might not play nice with.
 
Do the manual alignment, it's simply and once you align and tell ZFS to use 4k sectors you never have to do it again since the pool will retain that information. Or you can leave it not aligned and only loose a small amount of performance. I bench marked my 5x 2TB Samsung's both before and after alignment, and it wasn't a huge increase in performance, even miss-aligned in a RAIDz pool it could still saturate GigE Ethernet a couple times over so it's not a huge deal.
 
Funnily enough, I jsut noticed that the two new drives I put into OpenIndiana were automatically created with the correct ashift. I haven't migrated the old drives over yet (and I will need to re-create their pool), but at least it did it correctly for the new ones. Once I know what it does with the old drives, I will post the results - it iwll be interesting to see if it is the distro doing things right, or the drives themselves that make the difference. New drives are these: 2 x Seagate Barracuda Green SATA 6Gb/s 2TB Hard Drive
 
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