vinum in 4.x poor performer?

[Dan Nelson]

In the last episode (Feb 09), Marc G. Fournier said:
> On Wed, 9 Feb 2005, Greg 'groggy' Lehey wrote:
> >On Tuesday,  8 February 2005 at 23:21:54 -0400, Marc G. Fournier wrote:
> >>I have a Dual-Xeon server with 4G of RAM, with its primary file
> >>system consisting of 4x73G SCSI drives running RAID5 using vinum
> >>... the operating system is currently FreeBSD 4.10-STABLE #1: Fri
> >>Oct 22 15:06:55 ADT 2004 ... swap usage is 0% (6149) ... and it
> >>performs worse then any of my other servers, and I have less
> >>running on it then the other servers ...
> >>
> >>I also have HTT disabled on this server ... and softupdates enabled
> >>on the file system ...
> >>
> >>That said ... am I hitting limits of software raid or is there
> >>something I should be looking at as far as performance is
> >>concerned?  Maybe something I have misconfigured?
> >
> >Based on what you've said, it's impossible to tell.  Details would
> >be handy.
> 
> Like?  I'm not sure what would be useful for this one ... I just sent
> in my current drive config ... something else useful?

Details on the array's performance, I think.  Software RAID5 will
definitely have poor write performance (logging disks solve that
problem but vinum doesn't do that), but should have excellent read
rates.  From this output, however:
 
> systat -v output help:
>     4 users    Load  4.64  5.58  5.77             

> Proc:r  p  d  s  w    Csw  Trp  Sys  Int  Sof  Flt
>     24     9282       949 8414*****  678  349 8198

> 54.6%Sys   0.2%Intr 45.2%User  0.0%Nice  0.0%Idl  

> Disks   da0   da1   da2   da3   da4 pass0 pass1   
> KB/t   5.32  9.50 12.52 16.00  9.00  0.00  0.00   
> tps      23     2     4     3     1     0     0   
> MB/s   0.12  0.01  0.05  0.04  0.01  0.00  0.00   
> % busy    3     1     1     1     0     0     0   

, it looks like your disks aren't being touched at all.  You are doing
over 99999 syscalls/second, though, which is mighty high.  The 50% Sys
doesn't look good either.  You may have a runaway process doing some
syscall over and over.  If this is not an MPSAFE syscall (see
/sys/kern/syscalls.master ), it will also prevent other processes from
making non-MPSAFE syscalls, and in 4.x that's most of them.

-- 
	Dan Nelson
	dnelson at allantgroup.com