From: Nikolai Grigoriev <ngrigoriev@gmail.com>
To: linux-btrfs@vger.kernel.org
Subject: Re: ext4 vs btrfs performance on SSD array
Date: Wed, 27 Aug 2014 21:59:50 +0000 (UTC) [thread overview]
Message-ID: <loom.20140827T235422-162@post.gmane.org> (raw)
In-Reply-To: pan$646f5$964a0f2f$c0fb64a3$d18066b7@cox.net
Duncan <1i5t5.duncan <at> cox.net> writes:
>
> Nikolai Grigoriev posted on Tue, 26 Aug 2014 19:39:08 -0400 as excerpted:
>
> > Kernel: 3.8.13-35.3.5.el6uek.x86_64 #2 SMP Fri Aug 8 21:58:11 PDT 2014
> > x86_64 x86_64 x86_64 GNU/Linux
>
> > Btrfs v0.20-rc1
>
> I've no answer for your question, but you know how old both your kernel
> and btrfs-progs versions are, for a filesystem under as heavy development
> as btrfs is, right?
Yes. As much as I'd like to run latest & greatest the company sticks to OEL
6.5 so I have to play within the limits. The primary reason why I asked the
question is because I have noticed that "btrfs does it much better :)" and
wanted to understand why. Either to understand ext4 limitations vs btrfs or
to understand the issues with my ext4 configuration.
Actually, I have found the answer later last night. I have found that btrfs
has its own readahead implementation. So I've got an idea to disable it and
see if it makes it slower. And, indeed, I can confirm that in my specific
test scenario the readahead with 4Mb (default) buffer was making lots of
difference. I think it was mostly due to RAID-0 with 2 SSDs. But even on a
single filesystem it does make a difference.
Then I have also realized that since it was due to readahead, it won't be a
big game changer for Cassandra as it does lots of random reads.
But thanks anyway for the detailed explanation of BTRFS status. I'll surely
use it as soon as I can.
next prev parent reply other threads:[~2014-08-27 22:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-26 23:39 ext4 vs btrfs performance on SSD array Nikolai Grigoriev
2014-08-27 7:10 ` Duncan
2014-08-27 21:59 ` Nikolai Grigoriev [this message]
2014-09-02 0:08 ` Dave Chinner
2014-09-02 1:22 ` Christoph Hellwig
2014-09-02 11:31 ` Theodore Ts'o
2014-09-02 14:20 ` Jan Kara
2014-09-02 14:55 ` Theodore Ts'o
2014-09-02 12:55 ` Zack Coffey
2014-09-02 13:40 ` Austin S Hemmelgarn
2014-09-03 0:01 ` NeilBrown
2014-09-05 16:08 ` Christoph Hellwig
2014-09-05 16:40 ` Jeff Moyer
2014-09-05 16:50 ` Jens Axboe
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