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SubjectRe: mdadm software raid + ext4, capped at ~350MiB/s limitation/bug?

On Sun, 28 Feb 2010, Bill Davidsen wrote:

> Justin Piszcz wrote:
>> On Sun, 28 Feb 2010, Mike Snitzer wrote:
>>> On Sun, Feb 28, 2010 at 4:45 AM, Justin Piszcz <>
>>> wrote:
>> [ .. ]
>>> How did you format the ext3 and ext4 filesystems?
>>> Did you use mkfs.ext[34] -E stride and stripe-width accordingly?
>>> AFAIK even older versions of mkfs.xfs will probe for this info but
>>> older mkfs.ext[34] won't (though new versions of mkfs.ext[34] will,
>>> using the Linux "topology" info).
>> Yes and it did not make any difference:
>> Incase anyone else wants to try too, you can calculate by hand, or if you
>> are in a hurry, I found this useful:
>> I believe there is something fundamentally wrong with ext4 when performing
>> large sequential I/O when writing, esp. after Ted's comments.
>> Justin.
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> I'm going to have to do some testing now, I just tested ext4 against the raw
> speed of the device (single device test) and they were quite close to
> identical. I'm going to order one more drive to bring my test setup up to
> five devices, and do some testing on how it behaves.
> More later.

Thanks, let me know how it goes, I see the same thing, on a single hard
drive, there is little difference between EXT4 and XFS:

However, when multiple disks are involved, it is a different story.


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