raid3 is slow

[Eric Anderson]

On 03/28/07 07:25, Szabó Péter wrote:
> Yes, consumers are the disks.

[..snip..]

> #systat -vmstat
> 
>     4 users    Load  1.62  1.75  1.82                  Mar 28 14:24
> 
> Mem:KB    REAL            VIRTUAL                     VN PAGER  SWAP PAGER
>         Tot   Share      Tot    Share    Free         in  out     in  out
> Act   66488    6968   150740    11396   31172 count
> All 1017076   10160975701764    16256         pages
>                                                         1 zfod   Interrupts
> Proc:r  p  d  s  w    Csw  Trp  Sys  Int  Sof  Flt        cow    4066 total
>            1 60      9820  68312106 4237  752    1 195968 wire   1002 0: clk
>                                                     79088 act     128 8: rtc
> 89.2%Sys   3.0%Intr  3.3%User  0.0%Nice  4.5%Idl   714076 inact    10 10: 
> fxp
> |    |    |    |    |    |    |    |    |    |      29068 cache  1780 11: 
> ata
> =============================================+>>     2104 free    573 14: 
> ata
>                                                        12 daefr   573 15: 
> ata
> Namei         Name-cache    Dir-cache                     prcfr
>     Calls     hits    %     hits    %                     react
>        11       10   91                                 1 pdwake
>                                                      4045 pdpgs
> Disks   ad0   ad1   ad2   ad3   ad6                       intrn
> KB/t   8.42  8.42  8.42  8.42  5.67                113904 buf
> tps     287   287   287   287  1780                   133 dirtybuf
> MB/s   2.36  2.36  2.36  2.36  9.85                 69984 desiredvnodes
> % busy   25    26    24    26    99                 21586 numvnodes
>                                                     17495 freevnodes
> 
> I use mc to copy.
> 
> Matyee


Can you send the output of:

diskinfo -vt /dev/raid3/nmivol
diskinfo -vt /dev/label/nmivol1

Thanks
Eric



>> Szabó Péter wrote:
>>
>>> I have a raid3 setup with 5 consumers. it seems everything is all right, 
>>> but riad is very slow imho, but i don't have any >reference.
>> You need to give more accurate information. What are the "consumers" you
>> mention? Maybe you mean the disks/components of the RAID?
>>
>>> Now i copy from raid3 to a single hdd 75GB data. Nothing else run, except 
>>> ssh, and ftp. Before the copy my load is >0.1, after i star the copy the 
>>> load is 2.92 or higher, and the machine is very slow. I think this is not 
>>> normal, or is it?
>>> Copy how? By "cp" from shell?
>>> My config is:
>>> AMD Barton 2500+ with 1GB memory.
>>>
>>> I stop the copy, load is 0.05, and start again, after a few seconds load 
>>> is 2.02.
> 
>> Due to the way raid3 works, it's by definition more CPU-intensive than
>> most other RAID levels, but it shouldn't be even remotely slow as that.
>> Also, since your load is > 2, what are the other CPU intensive tasks?
> 
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