Re: [zfs-discuss] [zfs-code] Peak every 4-5 second

[Tharindu Rukshan Bamunuarachchi]

10,000 x 700 = 7MB per second ...... We have this rate for whole day .... 10,000 orders per second is minimum requirments of modern day stock exchanges ... Cache still help us for ~1 hours, but after that who will help us ... We are using 2540 for current testing ... I have tried same with 6140, but no significant improvement ... only one or two hours ... Robert Milkowski wrote: Hello Tharindu, Wednesday, July 23, 2008, 6:35:33 AM, you wrote: TRB> Dear Mark/All, TRB> Our trading system is writing to local and/or array volume at 10k TRB> messages per second. TRB> Each message is about 700bytes in size. TRB> Before ZFS, we used UFS. TRB> Even with UFS, there was evey 5 second peak due to fsflush invocation. TRB> However each peak is about ~5ms. TRB> Our application can not recover from such higher latency. TRB> So we used several tuning parameters (tune_r_* and autoup) to decrease TRB> the flush interval. TRB> As a result peaks came down to ~1.5ms. But it is still too high for our TRB> application. TRB> I believe, if we could reduce ZFS sync interval down to ~1s, peaks will TRB> be reduced to ~1ms or less. TRB> We like <1ms peaks per second than 5ms peak per 5 second :-) TRB> Are there any tunable, so i can reduce ZFS sync interval. TRB> If there is no any tunable, can not I use "mdb" for the job ...? TRB> This is not general and we are ok with increased I/O rate. TRB> Please advice/help. txt_time/D btw: 10,000 * 700 = ~7MB What's your storage subsystem? Any, even small, raid device with write cache should help.

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