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Date: Fri, 13 Feb 2015 14:08:33 +0100
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Subject: Re: btrfs performance, sudden drop to 0 IOPs
From: "P. Remek" <p.remek1@googlemail.com>
To: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: Kai Krakow <hurikhan77@gmail.com>, linux-btrfs@vger.kernel.org
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> I'd definitely suggest using NOCOW for any file you are doing O_DIRECT with,
> as you should see _much_ better performance that way, and also don't run the
> (theoretical) risk of some of the same types of corruption that swapfiles on
> BTRFS can cause.

I mounted the filesystem with nodatacow as follows and it didn't help
- it still drops to 0 IOPs every couple of seconds.

/dev/sdi on /mnt/btrfs type btrfs (rw,nodatacow)