[Littleguru]

Hi

I am creating 250 GB jfs file system on AIX 4.3.1 ,
but IBM recommends 2MB of jfslog for each 1GB of filesystem.
so I should create 2 jfslog for 250 GB of filesystem,
but how I can assign two jfslog to one filesystem ?
and in future how can I add more jfslog to filesystem ?

Thanks

[loot]

You can create as many jfslog as you want.
When you create a filesystem, you can specify the jfslog that you want to use.
Example:

crfs -v jfs -d mylv -m /my_mount_point -a logname=my_jfslog_lv

[Littleguru]

can I specify two jfslog for one filesystem:
crfs -v jfs -d mylv -m /my_mount_point -a logname=first_jfslog_lv,second_jfslog_lv

and what about if I want to increase the file system in future
so if I have 500 GB filesystem , I should have 4 jfslog and asign
it to this filesystem, because IBM recommends 2MB jfslog for
each 2GB filesystem.

[cdelgadop]

Hi

I think there's a confussion here. IBM recommendation for sizing jfslog devices is a rule of thumb and is intended to avoid lack of integrity when LVM tries to log changes to JFS2 FS. The rule says that you need to define a jfs2log and its size should be 2MB for each GB of data to be logged. So, if you have a FS of 10GB, you should have a jfs2log of 20MB; if you have a FS of 100GB, then your jfs2log should have at least 200MB, and so on.

Best recommendation for such enviroments os to have the jfslog device on different disk from the FS being protected.

Hope this helps

[Littleguru]

Thanks for help,
I created the jfs file system and every thing looks good.

[PaulClayton]

Depending on the purpose of your filesystem, you could use and INLINE log. This will grow or shrink as you increase or reduce your file system. IT has its advantages, but if the FS is used for a database, then using log volumes is the better option. Optimally I have found using a single log volume per file system, and as suggested using the log volume on another disk.

[ross.mather]

Paul, I don't think INLINE logging is an option on AIX 4.3.1 that the question was about. In fact I think its only available on jfs2....

[seth]

The question is what you want to do with this jfs file system? This 1GB to 1MB thing might be a nice hint but its absolute nonsense when you have 64 GB dbf Files in your 250 GB file system in this case I think a log device with 10 MB is still to big. On the other side when your FS has a large tree of 1k files the 1GB:1MB formula might not fit. Just try it, log devices can be increased an that during activity.

Cheers seth