[linux-lvm] Performance problem.

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Mon Nov 17 12:24:01 UTC 2003

>>      Actually.  SMB  never gives optimal transfer speeds. On a HUB you
>>      can  expect  not  much more than 6-7MB/S on a 100mbit connection.
>>      With  a  Switch  you can get higher, up to 12.5MB/s over FTP (but
>>      never with SMB due to protocol overhead etc).

> yeah, I thought it was smb at first aswell, but I get the exact
> same speed over ftp.  And rm'ing a file (on ssh to the server) and
> playing a mp3 at the same time shouldn't make the mp3 skip 1-3
> seconds should it?

  No,  that  is  true.  Your low read speed does indicate that you are
  not  using  DMA.  Give  us  the  output of "hdparm /dev/hda". Also a
  simple  benchmark is to do "dd_rescue /dev/hda /dev/null". What does
  that give you in numbers?

> And I've had a stable 11mb/sec out of smb before (tweaked).

>> Also there is this tool called elvtune. It allowes you to "tune the I/O
>> elevator per blockdevice queue basis". See the man pages.
>> You could try to lower the read latency for the affected devices (/dev/hda,
>> /dev/hdb, etc.)

> elvtune shows read_latency of 2048 and write_latency of 8192,
> that's already quite low isn't it?  If not, have any example values
> I can test with?

> cat .config | grep -i tcq shows 
> # CONFIG_BLK_DEV_IDE_TCQ is not set
> should I manually set it and compile?  It's not in make_config.

  You can try. Though I suspect you will not gain much speed.

> also does anyone have a lvmcreate_initrd script for lvm2?

> just did a bonnie++ test on the lvm volume.  Seems VERY slow doesen't it.

> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> hollowtube       1G  3787  93 26948  62 10841  14  5885  90 21274 17 175.3   1
>                     ------Sequential Create------ --------Random Create--------
>                     -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>               files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                  16  4991  98 +++++ +++  4135  90  4613  91 +++++ +++  3912  89
> hollowtube,1G,3787,93,26948,62,10841,14,5885,90,21274,17,175.3,1,16,4991,98,+++++,+++,4135,90,4613,91,+++++,+++,3912,89

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