Date: Thu, 6 Jan 2011 20:45:31 +0100 From: Damien Fleuriot <ml@my.gd> To: Daniel Kalchev <daniel@digsys.bg> Cc: freebsd-stable@freebsd.org Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks Message-ID: <AANLkTim7%2Bic_qB8vuod=CikV_3innwckECFWCE4kj%2Bvu@mail.gmail.com> In-Reply-To: <4D25C760.4070703@digsys.bg> References: <4D1C6F90.3080206@my.gd> <ifsia5$5ub$2@dough.gmane.org> <4D21E679.80002@my.gd> <84882169-0461-480F-8B4C-58E794BCC8E6@my.gd> <BEBC15BA440AB24484C067A3A9D38D7E0149F32D13E3@server7.acsi.ca> <488AE93A-97B9-4F01-AD0A-0098E4B329C3@my.gd> <AANLkTimezasVY%2BMJjWn2T9sBGQV-JrNmYqRwv_gPYPJP@mail.gmail.com> <CC37553B-EE13-4B5B-AC87-80D0ECC1A2B3@my.gd> <BEBC15BA440AB24484C067A3A9D38D7E0149F32D33F9@server7.acsi.ca> <4D25BF91.7070304@my.gd> <4D25C760.4070703@digsys.bg>
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On 6 January 2011 14:45, Daniel Kalchev <daniel@digsys.bg> wrote: > For pure storage, that is a place you send/store files, you don't really > need the ZIL. You also need the L2ARC only if you read over and over again > the same dataset, which is larger than the available ARC (ZFS cache memory). > Both will not be significant for 'backup server' application, because it's > very unlikely to do lots of SYNC I/O (where separate ZIL helps), or serve > the same files back (where the L2ARC might help). > > You should also know that having large L2ARC requires that you also have > larger ARC, because there are data pointers in the ARC that point to the > L2ARC data. Someone will do good to the community to publish some reasonable > estimates of the memory needs, so that people do not end up with large but > unusable L2ARC setups. > > It seems that the upcoming v28 ZFS will help greatly with the ZIL in the > main pool.. > > You need to experiment with the L2ARC (this is safe with current v14 and v15 > pools) to see if your usage will see benefit from it's use. Experimenting > with ZIL currently requires that you recreate the pool. With the > experimental v28 code things are much easier. > I see, thanks for the pointers. The thing is, this will be a home storage (samba share, media server) box, but I'd also like to experiment a bit, and it seems like a waste to not try at least the cache, seeing I'll have a SSD at hand. If things go well, I may be able to recommend ZFS for production storage servers at work and I'd really like to know how the cache and ZIL work at that time ;)
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