XServe RAID journaling

[Brad Bussé]

Oh yeah, another question:

Apple recommends using 128bit blocking for media drives. My current XServe RAID is set at 256bit blocks for each RAID 5, and the RAID 0 stripe of those two is set at 32bit blocks. Does this sound about right, or should I change something?

[Tony! Hulette]

[Saddler] “So I’ve heard conflicting reports over journaling of media drives over the past year. Some say it has a significant hit on performance, and others say it’s negligible. What’s the most current info. on this?

And, if journaling an XServe RAID set as RAID 50, are you supposed to journal just the individual RAID 5 groupings of 7 drives each, or just the RAID 0 stripe of the RAID 5 groups, or all? “

I recommend you DO NOT have journaling turned on if you’re using your RAID for video. It can and probably will cause dropped frames or other problems. The only place you deal with journaling is in Disk Utility when you go to create the 0 part of your 50 RAID. So that is where you want to be sure and not use journaling.

Also in RAID admin be sure and turn on controller and drive write cache options, and turn off “Allow host cache flushing” and “Use Steady Streaming Mode.”

For the read prefetch I set it to 8 stripes (in RAID Admin), and in Disk Utility I set the blocks to 128k (although, the default 32k seems to work fine form most/all applications).

Hope that helps