Fron the zpool man page: By default, the intent log is allocated from blocks within the main pool. However, it might be possible to get better performance using separate intent log devices such as NVRAM or a dedicated disk.
I was also contemplating the idea of a fast SSD on PCIe as a ZIL and L2ARC. And given the fact that the SSD will not suffer from the different types and locations of IO requests, maybe it makes sense to go with a big SSD, and partition it for a small ZIL partition, and the rest for L2ARC. Anyone tried that? Regards, Nikolay On Aug 29, 2012, at 2:47 AM, Andrew Young <ayo...@mosaicarchive.com> wrote: > Thanks for the great feedback Josh! The optimum size for an ssd zil device > was still an open question for us. I'm really glad to hear that they don't > need to be that big. > > What does zfs do with the zil if there is no dedicated zil device? Our > servers consist of a small sata drive that holds the OS and a boatload of > larger drives on a sas bus. What I'm wondering is if I simply replace the OS > disk with an ssd will I get the same performance boost as if I added a > dedicated ssd zil? > > Thanks! > Andy > > On Aug 28, 2012, at 7:07 PM, Josh Paetzel <j...@tcbug.org> wrote: > >>>> -------- Original Message -------- >>>> Subject: Support for Fusion IO drives? >>>> Date: Tue, 28 Aug 2012 16:46:00 -0400 >>>> From: Andy Young <ayo...@mosaicarchive.com> >>>> To: freebsd-hardware@freebsd.org >>>> >>>> >>>> We are investigating adding SSDs as ZIL devices to boost our ZFS write >>>> performance. I read an article a while ago about iX Systems teaming up >>>> with >>>> Fusion IO to integrate their hardware with FreeBSD. Does anyone know >>>> anything about supported drivers for Fusion IO's iodrives? >>>> >>>> Thanks! >>>> >>>> Andy >>>> _______________________________________________ >>>> freebsd-hardware@freebsd.org mailing list >>>> http://lists.freebsd.org/mailman/listinfo/freebsd-hardware >>>> To unsubscribe, send any mail to >>>> "freebsd-hardware-unsubscr...@freebsd.org" >>>> >>>> >>>> >>>> >> >> I'll put on my iXsystems hat here, as well as my fast storage, ZFS and >> Fusion-I/O hat. >> >> The ZFS filesystem supports dedicated ZIL devices, which can accelerate >> certain types of write requests, notably related to fsync. The VMWare >> NFS client issues a sync with every write, and most databases do as >> well. In those types of environments having a fast dedicated ZIL device >> is almost essential. In other environments the benefits of a dedicated >> ZIL range from non-existent to substantial. >> >> A good dedicated ZIL device is all about latency. It doesn't need to be >> large, in fact it will only ever handle 10 seconds of writes, so 10x >> network bandwidth is worst case. (In most environments this means 20GB >> is larger than needed). >> >> Fusion-I/O cards are far too large to be cost effective ZIL devices. >> Even though they do rock at I/O latency, the really fast ones are also >> fairly large, so the $/GB on them isn't so attractive. There are better >> options for ZIL devices. >> >> Another consideration is the Fusion-I/O driver is fairly memory hungry, >> which competes with memory ZFS wants to use for read caching. >> >> Now as an L2ARC device, that's a whole different can of worms. >> >> Command line used: iozone -r 4k -s 96g -i 0 -i 1 -i 2 -t 8 >> Parent sees throughput for 8 readers = 1712399.95 KB/sec >> L2 ARC Breakdown: 197.45m >> Hit Ratio: 98.61% 194.71m >> L2 ARC Size: (Adaptive) 771.13 GiB >> ARC Efficiency: 683.40m >> Actual Hit Ratio: 71.09% 485.82m >> >> ~ 800GB test data, all served from cache. >> >> If you are considering Fusion-I/O, the FreeBSD driver is generally not >> released to the general public by Fusion-I/O, but can be obtained from >> various partners. (I believe iXsystems is the only FreeBSD friendly >> fusion-i/o partner but could be wrong about that) >> >> >> -- >> Thanks, >> >> Josh Paetzel >> > _______________________________________________ > freebsd-hardware@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hardware > To unsubscribe, send any mail to "freebsd-hardware-unsubscr...@freebsd.org" _______________________________________________ freebsd-hardware@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hardware To unsubscribe, send any mail to "freebsd-hardware-unsubscr...@freebsd.org"