PermaLink Performance Tuning Lotus Domino Transaction Logging12/06/2006 11:25 AM
IBM Lotus Domino can use Transaction Logging circular, to prevent data loss or data corruption in case of a server crash, or archive style. This allows use of certified backup software that will frequently store the translogs in addition to eg weekly full-backups to save diskspace compared to daily full-backups. Of course this configuraiton requires correct configuration and you should think about performance BEFORE implementing.

As documented in the Administration Help, Transaction Logging data requires a dedicated disk (not a LUN or a partition). To make this clear: a dedicated disk is used for this purpose ONLY and for nothing else. Nobody will help you if you see bad performance on your Domino server if you do not meet this requirement.

Domino will write data in 16 K blocks to the translog disk, read access only happens in case of a restore (roll forward) and during backing up. If you are optimising for Domino performance you should try to optimize write performance on your translog disk. Make sure you have all write caches enabled on the disk and the controller. This is a screenshot showing the write cache configuration of an IBM fibre channel controller:

If you are using a SAN, like IBM FastT Storage, you have several parameters to configure. Let's have a look at a SAN:

In this case we see several RAID 5 arrays. RAID 5 is a cheap solution to have data redundant on disks so you can loose ONE disk without data loss. RAID 1 (mirroring) is more expensive as you need more disks but is faster than RAID 5. In a SAN like the FAStT you will see only low performance impact of RAID 5 as the controller is very fast, this does usually not apply to cheaper NAS solutions or software RAIDs.

You can configure each LUN individually:

In this case we have write cache (with batteries) enabled but the block size/segment size of 512K is not the best choice for Domino Transactionlogs. Try using 16K instead. Note: This does not apply to Domino databases where a block size of 4K (or 8K if 4K is not available) should be used.

Very important: When attaching the storage to your Domino Servers OS be sure to format the LUN with a block size exactly matching the one you configured on the storage!

If your SAN support monitoring you can check the current load:

For preparing my next Blog entry I would like to know your performance data:
- What is your Domino Servers read percentage for databases (not translog)?
- What is your block size for domino data and does the maximum KB/second match what you can expect from the physical disks?

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