EXT3 Users Mailing List

Andrey | 23 Sep 2011 11:52

Re: ext3 with maildir++ = huge disk latency and high load

Thank you for reply,

BTW, other webserver has almost the same bonnie results (10283ms and 
5884ms) on ext3 partition with 45GB of data (1.5 millions of files)?!

Hardware and RAID5(also hardware) are the same: HP Proliant DL380 G4 
with SmartArray 6i controller (as I see it comes with 128MB BBWC enabler 
but not kit).

I did not tried to mount fs with barriers disabled. Does it have any 
crititcal risks?

Bonnie tests was performed in the morning when we have a mininmal user load.

But why the same server with the same RAID(4 disks) but with FreeBSD+UFS 
was much better? I guess problem is in ext3 then?

With regards, Andrey.

23.09.2011 11:31, Janne Pikkarainen пишет:
> Hello,
>
> On 09/23/2011 08:51 AM, Andrey wrote:
>> Hello,
>>
>> I have a production mail server with maildir++ structure and about
>> 250GB (~10 millions) of files on the ext3 partition on RAID5. It's
>> mounted with noatime option. These mail server is responsible to local
>> delivery and storing mail messages.
>>

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Eric Sandeen | 23 Sep 2011 16:43

Re: ext3 with maildir++ = huge disk latency and high load

On 9/23/11 4:52 AM, Andrey wrote:
> Thank you for reply,
> 
> BTW, other webserver has almost the same bonnie results (10283ms and
> 5884ms) on ext3 partition with 45GB of data (1.5 millions of
> files)?!
> 
> Hardware and RAID5(also hardware) are the same: HP Proliant DL380 G4
> with SmartArray 6i controller (as I see it comes with 128MB BBWC
> enabler but not kit).
> 
> I did not tried to mount fs with barriers disabled. Does it have any
> crititcal risks?

Yes.  If you have write caches on either the raid controller or on
the disks behind it which can be lost on a power outage, running
without barriers will potentially corrupt your filesystem if you lose
power, even though you have ext3's journaling.

Journaling depends on write guarantees which are lost if drive
write caches evaporate.

-Eric

> Bonnie tests was performed in the morning when we have a mininmal user load.
> 
> But why the same server with the same RAID(4 disks) but with FreeBSD+UFS was much better? I guess problem is
in ext3 then?
> 
> With regards, Andrey.

(Continue reading)

headers

Eric Sandeen | 23 Sep 2011 16:48

Re: ext3 with maildir++ = huge disk latency and high load

On 9/23/11 9:43 AM, Eric Sandeen wrote:
> On 9/23/11 4:52 AM, Andrey wrote:
>> Thank you for reply,
>>
>> BTW, other webserver has almost the same bonnie results (10283ms and
>> 5884ms) on ext3 partition with 45GB of data (1.5 millions of
>> files)?!
>>
>> Hardware and RAID5(also hardware) are the same: HP Proliant DL380 G4
>> with SmartArray 6i controller (as I see it comes with 128MB BBWC
>> enabler but not kit).
>>
>> I did not tried to mount fs with barriers disabled. Does it have any
>> crititcal risks?
> 
> Yes.  If you have write caches on either the raid controller or on
> the disks behind it which can be lost on a power outage, running
> without barriers will potentially corrupt your filesystem if you lose
> power, even though you have ext3's journaling.
> 
> Journaling depends on write guarantees which are lost if drive
> write caches evaporate.

... evaporate unexpectedly that is.  barriers manage that cache.

If write caches are battery-backed (or off), then nobarrier is safe.

-Eric

> -Eric

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