Date: Sat, 18 Feb 2012 23:48:07 +1000 From: Da Rock <freebsd-questions@herveybayaustralia.com.au> To: freebsd-questions@freebsd.org Subject: Re: /usr/home vs /home Message-ID: <4F3FAC17.8000300@herveybayaustralia.com.au> In-Reply-To: <4F3FA9FB.7030203@infracaninophile.co.uk> References: <4F3ECF23.5000706@fisglobal.com> <20120217234623.cf7e169c.freebsd@edvax.de> <3D08D03C85ACFBB1ABCDC5DA@mac-pro.magehandbook.com> <alpine.BSF.2.00.1202172316230.11247@abbf.6qbyyneqvnyhc.pbz> <20120218112252.772c878b.freebsd@edvax.de> <4F3F80FD.8070201@herveybayaustralia.com.au> <4F3F8A46.1090908@infracaninophile.co.uk> <4F3F8D39.80907@herveybayaustralia.com.au> <4F3FA9FB.7030203@infracaninophile.co.uk>
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On 02/18/12 23:39, Matthew Seaman wrote: > On 18/02/2012 11:36, Da Rock wrote: >> If I may, can I ask a quick question: My main misgivings about ZFS have >> been speed, ram use, and up till about a year ago or so relative 'youth' >> (at least on FreeBSD). What would be the minimum ram you would use for a >> high disk use? And what would be recommended to use for the caching? I >> was thinking 8G ram and either a high quality usb/SD(/CF?) disk or a >> sata II/III SSD for cache. > Yes -- ZFS uses RAM heavily to improve performance. I've a VM running > ZFS with only 1GB which is pretty slow. Mind you, a similar VM with > UFS is also pretty slow. > > For an actual machine, about 4GB makes a reasonable ZFS system. More is > better though; 8GB is what I'd recommend. ZFS speed is on the whole > pretty reasonable. It doesn't do small, randomized IO very effectively, > so it's not ideal to run a database on. Other than that, for a home > e-mail / web /fileserver ZFS is just fine. > > I haven't tried SSDs or anything like that -- that's an optimization to > improve latency when accessing lots of different files, and my usage > doesn't really justify it. Try it without before spending any money on > SSDs. It may well be good enough, but if it isn't then adding SSDs and > making ZFS use them for ZIL or cache is pretty simple (and doesn't > require any downtime.) I was thinking along the lines of continuous heavy load of writing (some read) rather large files (5G+ would be average - multiple!) - does that warrant caching or is it only lots of smaller files? That and lots of ~0.5G files (read mostly) is what defines the main load on the system. I ask because I'm not 100% sure of what the caching is for. I had thought it was like the journal log for fast writing to be later written to the filesystem itself, but now I think I may be wrong in my judgement. It now sounds like a fast access for usual suspects. Now you see how a terabyte and a half disk space can be used in a matter of hours :)
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