Originally posted by: apple08

dear AIX gurus,
would like to seek your advice.
whenever i create lv, i always create log lv, but has yet to know the best practise.
i heard last time to create log lv of the 1/8 size of your file system. if i have many file system mounted on it, can i associate all the file system to the same log lv? or need to create for each file system 1 log lv?
what is the purpose of having log? will it help us during disaster recovery? looking forward for you awaiting reply. thanks a lot

Originally posted by: kappa

Hi, Apple08!

It is a log space for Journal based FS, jfs and jfs2 are journal FS. Its only purpose is for faster fsck (FS checking) after accidents. It does not recover file data.

Never heard or read such nonsense. It's a journalling log, not a snapshot volume.

Some hints for usage:
You need at least one log lv per FS Type per VG. (jfslog vs. jfs2log)
You can have several FS pointing at the same log (=default) or give each FS its own log.
The default should be sufficient, give highly modified FS a separate log.
jfs2 allows inline logging without having a log lv, the journal log is "inside" the FS.

--jk

Originally posted by: apple08

dear aix gurus
very interesting.
give highly modified FS a separate log.
apple08> i have a very dumb question i think, but i'm very curious. how can we benchmark the highly modified FS among other FS? do we have something like file system log for us to determine this.

jfs2 allows inline logging without having a log lv, the journal log is "inside" the FS.
almond08> attached is one of our FS characteristic. we have jfs2 installed. meaning during our file system creation, i don't need to create log for the lv is it? please correct me if i get it wrong.
hope to hear from you. thanks a lot

Originally posted by: kappa

Hi,

you can use filemon (a system trace tool for i/o activity) and look for high %util of the log lv.

If you say yes for Inline Log attribute, then the new jfs2 FS does not need a log lv.
Thus, the log space is part of the LV containing the new FS.

btw: the inline log space defaults to 0.4% of FS space (and grows dyn. with the FS).

2nd update: You wrote 1/8 of FS size = 12.5%, this would be more than the max. allowed value: 10% (and/or 2047 MB)

Message was edited by: kappa

Originally posted by: apple08

interesting, will it degrade our file system performance as the log is within the file system itself? hope to hear from you. thanks a lot

Originally posted by: apple08

if i wanted to extend that filesystem (with inline log), can i just extend like normal? extend the vg and then extend the file system? hope to hear from you. thank you

Originally posted by: orphy

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds1/chfs.htm
Orphy

Originally posted by: apple08

dear mr orphy,
i'm using smit jfs2. i can change as normal right even i have inline log reside in the file system. hope to hear from you. thank you

Originally posted by: orphy

yes but you should read the man page
Orphy

Originally posted by: apple08

dear mr orphy,
i have read the notes.
quote the point:
6. When the new file system size is specified, but its inlinelog size is NOT specified, the new logsize will be adjusted (extended/shrunk) proportionally, based on the specified extended/shrunk file system size. The log size increase or reduction should not be more than 40% of the file system size increase or reduction.
meaning when we i issue smit jfs2, it'll adjust accordinly the inline log right?
please correct me if i'm wrong. thank you.

Originally posted by: orphy

You should have some confidence in yourself! If you are not sure, you can always create a test FS and try it out first. It's quite easy and doesn't take much time/effort to verify it yourself.
Orphy

Originally posted by: apple08

dear mr orphy,
i've tried this. it will change accordinly. i learn a lot from you. thank you.
Command: OK stdout: yes stderr: no

Before command completion, additional instructions may appear below.

Filesystem size changed to 655360
Inlinelog size changed to 3 MB.

Originally posted by: SystemAdmin

hi brother ,

the only thing you have to known is there is only one loglv for one vg ,it contains entire filesystem logs in that lv if loglv get correpted we have to recreate log using with logform command and you can check each filesystem consystency using fsck

Originally posted by: apple08

normally i create log lv when i'm creating the file system. i don't create loglv per vg. did i miss good step? hope to hear from you. thank you