linux-ext4 - Re: [zfs-discuss] ZFS, XFS, and EXT4 compared

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Message-id: <46D70D8C.8010203@sun.com>
Date:	Thu, 30 Aug 2007 14:33:48 -0400
From:	Jim Mauro <James.Mauro@....com>
To:	"Jeffrey W. Baker" <jwbaker@....org>
Cc:	zfs-discuss@...nsolaris.org, xfs@....sgi.com,
	linux-ext4@...r.kernel.org
Subject: Re: [zfs-discuss] ZFS, XFS, and EXT4 compared

I'll take a look at this. ZFS provides outstanding sequential IO performance
(both read and write). In my testing, I can essentially sustain 
"hardware speeds"
with ZFS on sequential loads. That is, assuming 30-60MB/sec per disk 
sequential
IO capability (depending on hitting inner or out cylinders), I get 
linear scale-up
on sequential loads as I add disks to a zpool, e.g. I can sustain 
250-300MB/sec
on a 6 disk zpool, and it's pretty consistent for raidz and raidz2.

Your numbers are in the 50-90MB/second range, or roughly 1/2 to 1/4 what was
measured on the other 2 file systems for the same test. Very odd.

Still looking...

Thanks,
/jim

Jeffrey W. Baker wrote:
> I have a lot of people whispering "zfs" in my virtual ear these days,
> and at the same time I have an irrational attachment to xfs based
> entirely on its lack of the 32000 subdirectory limit.  I'm not afraid of
> ext4's newness, since really a lot of that stuff has been in Lustre for
> years.  So a-benchmarking I went.  Results at the bottom:
>
> http://tastic.brillig.org/~jwb/zfs-xfs-ext4.html
>
> Short version: ext4 is awesome.  zfs has absurdly fast metadata
> operations but falls apart on sequential transfer.  xfs has great
> sequential transfer but really bad metadata ops, like 3 minutes to tar
> up the kernel.
>
> It would be nice if mke2fs would copy xfs's code for optimal layout on a
> software raid.  The mkfs defaults and the mdadm defaults interact badly.
>
> Postmark is somewhat bogus benchmark with some obvious quantization
> problems.
>
> Regards,
> jwb
>
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss@...nsolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
>   
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