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Re: ZFS, XFS, and EXT4 compared

To: "Jeffrey W. Baker" <jwbaker@xxxxxxx>
Subject: Re: ZFS, XFS, and EXT4 compared
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Thu, 30 Aug 2007 14:14:04 -0500
Cc: zfs-discuss@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx
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Jeffrey W. Baker wrote:
> On Thu, 2007-08-30 at 13:57 -0500, Eric Sandeen wrote:

>> barrier seems to hurt badly on xfs, too.  Note: barrier is off by
>> default on ext[34], so if you want apples to apples there, you need to
>> change one or the other filesystem's mount options.  If your write cache
>> is safe (battery backed?) you may as well turn barriers off.  I'm not
>> sure offhand who will react more poorly to an evaporating write cache
>> (with no barriers), ext4 or xfs...
> 
> I didn't compare the safety of the three filesystems, 

Understood

> but I did have
> disk caches disabled 

Oh, so for the SW raid tests the individual disks had no write cache?f

> and only battery-backed caches enabled.  Do you
> need barriers without volatile caches?

As far as I understand it, then nope, you don't need it, and you're
hurting performance with it.

-Eric


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