FS of choice for max random iops ( Maildir )

Terje Elde terje at elde.net
Fri Sep 16 21:22:48 UTC 2011

On 16. sep. 2011, at 16:18, freebsd at top-consulting.net wrote:

>  Got a measly 74MB/sec.

You can't ask for advice, get it, do something completely different, and then complain that it didn't work. 

Neither can you ask people to donate their time, if you won't spend yours. 

In other words: if you won't listen, there's no point in us talking. 


Don't disable ZIL. Just don't. It's not the way to go. If you want to know why, google will help. 

Also, you're making some assumptions, such as the ZIL being bad for performance. That's not always the case. ZIL-writes are a rather nice load for spinning metal storage. Even if you write through cache, that can give you a boost on your real world workload. 

Which brings us to the third bit. You're benchmarking, not trying real world loads. That's the load you'll have to worry about, and it's the load zfs shines at. 

Thanks to the ZIL (the thing you're trying to kill, remember?) you can convert seek heavy writes to sequential zil-writes, freeing up disk bandwith for concurrent reads. 

If you want to test before spending money, try what Svein said. Set up a small logical volume (preferrably smaller than your controller cache, if it's large enough), then try that as a dedicated zil-device. 

Never tried that, but worth a shot. 


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