Re: [Dump-users] Dump 10 times slower on faster system

[Bob B. Jr. <bl...@da...>]

On Wed, 2012-01-11 at 14:06 -0800, Steve Bonds wrote:
> On Wed, Jan 11, 2012 at 11:04 AM, Bob Blanchard Jr. blabj-at-dainty.ca
> |dump-users/gmail/sbonds| <2n2...@sn...> wrote:
> 
> ... trimmed ... 
>         All interfaces are SAS, I can do dd reads from tape at 150
>         MB/s from both systems.
>         
>         Trying to determine if this is kernel related (st module) or
>         dump related or ext3/4 related.
> 
> 
> It looks like you're on the right track with your dd read tests to the
> tape drive.  What about dd write tests to the tape drive and dd read
> tests from the disk partition?  If these are slow, then dump will
> never get any faster.

dd write tests to the tape are between 150 and 160 MB/s. dd reads from
disk around 150 - 180 MB/s

So with dump "out of the way", both systems are giving me at least 150
MB/s read/write speeds.

> I also recall some performance issues with older versions of dump--
> try the newest release (or even the CVS version) and see if the
> problem persists.  You were using 0.4b41 (2006) and current is 0.4b44.
> 


Surprisingly, the "older" 0.4b41 on ubuntu hardy is the blazingly fast
dump at 55 MB/s.  0.4b42 is slow.

I built 0.4b44 from source, and tried again on the ubuntu lucid machine
(where dumps are 10 times slower), and it is an improvement.. average
throughput is around 15 MB/s instead of 5MB/s.  But this is still
nowhere near the 55 MB/s I'm getting with dump 0.4b41.

Could it be slower due to ext4??  Unfortunately I don't have an ext3
partition on the lucid server to test 0.4b44.  I suppse I could try to
build 0.4b44 on hardy and try an ext3 dump.

-Bob