Date: Mon, 9 Dec 2013 08:15:13 +0100 (CET) From: =?ISO-8859-1?Q?Trond_Endrest=F8l?= <Trond.Endrestol@fagskolen.gjovik.no> To: Mark Felder <feld@FreeBSD.org> Cc: freebsd-stable@freebsd.org Subject: Re: Does FreeBSD's ZFS reserve 1/64 of the capacity for COW? Message-ID: <alpine.BSF.2.00.1312090813270.75198@mail.fig.ol.no> In-Reply-To: <1386350612.24515.56413717.7535920E@webmail.messagingengine.com> References: <alpine.BSF.2.00.1312061325420.75198@mail.fig.ol.no> <1386350612.24515.56413717.7535920E@webmail.messagingengine.com>
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On Fri, 6 Dec 2013 11:23-0600, Mark Felder wrote: > > > On Fri, Dec 6, 2013, at 6:46, Trond Endrestøl wrote: > > Hi, > > > > Today I came across "Becoming a ZFS Ninja Part 1" > > http://www.youtube.com/watch?v=tPsV_8k-aVU featuring Ben Rockwood who > > stated that ZFS reserves 1/64 of the capacity for COW safe-guarding. > > Fast forward to 00:49:44. Thus, one should take this fact into account > > when planning the storage capacity of your (larger) zpools. > > > > Does FreeBSD's ZFS also reserve 1/64 of the capacity for COW? > > > > If it's true, then I guess this should be noted in zpool(8) and in the > > Handbook. > > > > Well, the rule-of-thumb / urban legend tends to be "don't let your zpool > go over ~80% or you'll have severe performance issues" so I'm not sure > that statement is accurate or COW wouldn't be so painful when your pool > is over ~80%. I could be wrong though; I often am :-) As it turns out, you're in good company, I'm also wrong far too often. -- +-------------------------------+------------------------------------+ | Vennlig hilsen, | Best regards, | | Trond Endrestøl, | Trond Endrestøl, | | IT-ansvarlig, | System administrator, | | Fagskolen Innlandet, | Gjøvik Technical College, Norway, | | tlf. mob. 952 62 567, | Cellular...: +47 952 62 567, | | sentralbord 61 14 54 00. | Switchboard: +47 61 14 54 00. | +-------------------------------+------------------------------------+
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