Originally posted by: SystemAdmin

What is the recommended JFS2 log size? Currently, when a filesystem is created it creates the log as 1 PP (depending on what the PP size is), I am not certain if this is sufficient for a 250GB filesystem.

Is there an algorithm I should be following, or written document that states "filesystem gb = 1/8 log size"

TIA
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Originally posted by: andycor

IMHO it depends of the activity and not the size of the filesystem.

If you have a big filesystem but there are relatively few operations performing on it, one PP could be far enough.
Also, if you have a smaller file system with hard activity under an amount of operations per seconds view, maybe you need a bigger JFS2LOG to be capable of register all the operations.

Anyway, you can left the jfs2log with the default size and resize it later if you get the typical JFS2LOG WRAP error.

Regards,
Andres Cordoba
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Originally posted by: SystemAdmin

Thanks for the reply.

I am not familar with WRAP errors. Will they show up in the errpt?

My filesystem is used a lot (I/O). What is the procedure to increase the JFS2 log size?

Thanks in advance.
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Originally posted by: andycor

Well, you must umount the filesystem, extend the jfs2log lv, do a logform and mount the filesystem again. For example, suppose that your file system is /yourfilesystem and his corresponding jfs2log is loglv00:

umount /yourfilesystem
extend loglv00 1
logform /dev/loglv00
mount /yourfilesystem

Hope this helps.

Regards,
Andres Cordoba
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Originally posted by: KelleyCook

Our corporate policy, recommended by a visiting JFS2 architect was, unless we had a specific storage requirement, to just create all of our JFS2 filesystems with an INLINE log (default size setting) and not worry about the issue.

We have followed that policy and not had a catastrophic failure with any of our JFS2 filesystems.
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Originally posted by: SystemAdmin

We don't have any problems with our current settings, however we do have some performance problems on several high I/O intensive systems.

Therefore, I am asking, how should the JFS2 log size be calculated?


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Originally posted by: SystemAdmin

if you use INLINE the log size will grow with fs size change
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Originally posted by: Jim_Carstensen

IBM recommends 2MB per GB or 1 partition per 512 partitions as a baseline, and then increase it if you have wrap errors in the errpt.

http://www-1.ibm.com/support/docview.wss?uid=isg3T1000398

From personal experience, this is fine for most normal I/O loads. If you want to oversize it for when everything is going wrong and you have a blizzard of writes, a little bit goes a long way.

Since the needed log size is really a function of the number of writes, lv size only indirectly affects needed log size.

Cheers,
Jim
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