LZ1 compression on 6.5.6 – Does it replicate?

I’m doing some testing on my Domino 6.5.6 FP3 servers.

I’ve got a bunch of mailboxes that did not already have LZ1 compression enabled (mostly archive mailboxes and a few mailboxes scattered around on remote servers). Mostly, it’s been turned on, and it’s definitely turned on in all of our mail.boxes.

The only reason that it is not turned on for all mailboxes up to this point is that we had to disabled it in our OpenNTF1.7b template because we have a couple of Mac OSX users. When design would run on the server at 1AM every night, the LZ1 property would be turned on for these 2 Mac users even though, we had manually turned it off. It was weird since, technote 1176010 entitled “Which Database properties are affected by a Design Replace or Refresh” clearly indicates that LZ1 compression is only affected by design replace and not design refresh.

These Mac OSX users would have problems with their attachments. There used to be technote number 1193756 on the issue, but it’s gone now. IBM must have fixed the issue and removed the technote.

I’ve enabled LZ1 compression for all databases now with the admin client (advanced properties).

Now, I’ve set the DEBUG_ENABLE_LZ1_REPAIR=1 in our * Configuration document so that it gets written to the notes.ini of all of our servers.

Next, I’m testing running load compact -ZU on a few databases to see how much disk space we could save.

Compact -ZU upgrades the compression of existing attachments in a database from Huffman to LZ1.
compact -ZD downgrades that compression from LZ1 to Huffman.
Setting the Enable LZ1 compression database property only compresses attachments from that point forward.
See the technote 1084388 entitled “Switches for COMPACT server task for Domino”

Initial tests show that I could save anywhere from 85% to 95% of disk space and that it takes about 3 minutes per GB to run the compact -ZU.

I’m also showing that I need to run compact a second time withouth any switches because compact -ZU may upgrade the attachment compressed with Huffman to LZ1, but it actually makes the database size bigger than before I started.

This prompted me to wonder. Does the compression replicate? or do I have to do this for every database on every server?

Anybody know the answer?

One Response to “LZ1 compression on 6.5.6 – Does it replicate?”

  • Stacey says:

    We ran this on our servers and found that it did not replicate. The documents don’t seem to be modified at the Notes level so they are not replicated (no modification date).

    I think that it is running at the file system level to re-compress the attachments. So for the initial compact -ZU to convert attachments you need to run on all replica copies.

    Hope that helps.

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