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Low performance with a btrfs cache of 4 ssd samsung 840 evo


elfco

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im having some problems with a btrfs cache of 4 ssd samsung 840 evo in unraid

the performance is really really poor

https://gyazo.com/936a484279c5c211c8ec96a2d9ed14c4

 

i read that could be the align of the partition

but i dont know how to change it in unraid, i changed the align with fdisk but unraid change it back when i mounted the array...

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5 hours ago, elfco said:

but i dont know how to change it in unraid

You can't for now, the Samsung alignment issue has bee reported before and LT is already aware, don't know if a fix is planned soon though, still that's very poor performance even for non optimally aligned SSDs, are they being trimmed and what raid profile are you using?

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29 minutes ago, elfco said:

they are in btrfs,

I meant what kind of raid, 1, 0, 10, I assume you're using the default raid1

 

29 minutes ago, elfco said:

formated today and empthy so they are trimmed

If they where used before in another system you still need to trimmed them, unless they've been secure erased or similar, if they are trimmed there's likely something wrong with one or more of the SSDs, by coincident I have a couple of 840 EVOs on my test server, this is me writing to that pool using default raid1 on my test server:

 

54219823_Screenshot2018-11-3020_45_01.png.8df4b9ddaa73e67251e080c9b9d2d26d.png

 

160419239_Screenshot2018-11-3020_44_51.thumb.png.5bf87ed2268592c7e1dbac4efc6e6267.png

 

 

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