Date: Wed, 17 Jul 2013 10:51:17 +0100 From: krad <kraduk@gmail.com> To: Shane Ambler <FreeBSD@shaneware.biz> Cc: FreeBSD Questions <freebsd-questions@freebsd.org>, aurfalien <aurfalien@gmail.com> Subject: Re: to gmirror or to ZFS Message-ID: <CALfReyd92-Wkg1T2Y4wSX0oKD08oH0%2Bms5U5%2ByF5KxVUj%2B=Erg@mail.gmail.com> In-Reply-To: <51E51558.50302@ShaneWare.Biz> References: <4DFBC539-3CCC-4B9B-AB62-7BB846F18530@gmail.com> <alpine.BSF.2.00.1307152211180.74094@wonkity.com> <976836C5-F790-4D55-A80C-5944E8BC2575@gmail.com> <51E51558.50302@ShaneWare.Biz>
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You would in theory as from what i remember every zfs filesystem takes up 64 kb of ram, so the savings could be massive 8) On 16 July 2013 10:41, Shane Ambler <FreeBSD@shaneware.biz> wrote: > On 16/07/2013 14:41, aurfalien wrote: > >> >> On Jul 15, 2013, at 9:23 PM, Warren Block wrote: >> >> On Mon, 15 Jul 2013, aurfalien wrote: >>> >>> ... thats the question :) >>>> >>>> At any rate, I'm building a rather large 100+TB NAS using ZFS. >>>> >>>> However for my OS, should I also ZFS or simply gmirror as I've a >>>> dedicated pair of 256GB SSD drives for it. I didn't ask for SSD >>>> sys drives, this system just came with em. >>>> >>>> This is more of a best practices q. >>>> >>> >>> ZFS has data integrity checking, gmirror has low RAM overhead. >>> gmirror is, at present, restricted to MBR partitioning due to >>> metadata conflicts with GPT, so 2TB is the maximum size. >>> >>> Best practices... depends on your use. gmirror for the system >>> leaves more RAM for ZFS. >>> >> >> Perfect, thanks Warren. >> >> Just what I was looking for. >> > > I doubt that you would save any ram having the os on a non-zfs drive as > you will already be using zfs chances are that non-zfs drives would only > increase ram usage by adding a second cache. zfs uses it's own cache > system and isn't going to share it's cache with other system managed > drives. I'm not actually certain if the system cache still sits above > zfs cache or not, I think I read it bypasses the traditional drive cache. > > For zfs cache you can set the max usage by adjusting vfs.zfs.arc_max > that is a system wide setting and isn't going to increase if you have > two zpools. > > Tip: set the arc_max value - by default zfs will use all physical ram > for cache, set it to be sure you have enough ram left for any services > you want running. > > Have you considered using one or both SSD drives with zfs? They can be > added as cache or log devices to help performance. > See man zpool under Intent Log and Cache Devices. > > > ______________________________**_________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/**mailman/listinfo/freebsd-**questions<http://lists.freebsd.org/mailman/listinfo/freebsd-questions>; > To unsubscribe, send any mail to "freebsd-questions-** > unsubscribe@freebsd.org <freebsd-questions-unsubscribe@freebsd.org>" >
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