mirror jfslog question

mirror jfslog question

Post by Mwedelste » Mon, 19 Mar 2001 11:20:21



Hello,
  On aix 4.3.3 we have a second volume group that consists of a mirrored
logical volume and an unmirrored jfslog and paging space. Should we mirror the
jfslog? And if so, can it be done while the system is being accessed (ie via
smit or the mklvcopy command)? Any details would be greatly appreciated.

Thankyou,
Mike Edelstein, Zytek Inc.

 
 
 

mirror jfslog question

Post by Christer Pal » Mon, 19 Mar 2001 22:14:01



>   On aix 4.3.3 we have a second volume group that consists of a mirrored
> logical volume and an unmirrored jfslog and paging space. Should we mirror the
> jfslog?

If that jfslog is used by a mirrored filesystem, yes, absolutely!
Otherwise you will lose access to the filesystem if the disk containing
the jfs log goes offline.

Similarly, you'd probably want to mirror all paging spaces. Losing
access to a paging space will most likely cause the system to crash.

Quote:

> And if so, can it be done while the system is being accessed (ie via
> smit or the mklvcopy command)? Any details would be greatly appreciated.

Yes - just use mklvcopy.

  palm.vcf
< 1K Download

 
 
 

1. Mirroring, mwc and jfslog question?

Hi,

What is the recommendations for Mirror Write Consistency on type
'jfslog' volume groups. A clean AIX 4.3.3 install has MWC turned on for
all logical volumes except the paging and jfslog LV's. If i use the
'mirrorvg' command to mirror the rootvg, it will complain about quorum
and other stuff, but never mention or change the MWC state.

I ask this because i've just had a look at a DB2 server with some
performance problems, and found that one of the jfslog LV's has MWC
turned on, and looking on iostat etc. the discs (BTW: SSA discs) with
this LV seems to take a major performance hit (lots of iowait etc...)
compared to the other discs in this VG.

My first suggestion would be to turn the MWC off on the jfslog, and move
this to the center location on the disc (maybe even seperate discs). The
jfs LV remains with MWC turned on.

The redbook 'Database performance on AIX...' talks a little about MWC,
but only in relation to data LV's not the jfslog's...

any suggestions welcome...

TIA,
Jesper James

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