Date: Fri, 16 May 2014 09:34:12 -0500 From: Karl Denninger <karl@denninger.net> To: freebsd-stable@freebsd.org Subject: Re: gmirror + ZFS issues Message-ID: <537621E4.1000907@denninger.net> In-Reply-To: <53761E51.9060908@boiteameuh.org> References: <5376115D.5050704@boiteameuh.org> <53761477.70205@denninger.net> <53761E51.9060908@boiteameuh.org>
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[-- Attachment #1 --] On 5/16/2014 9:18 AM, Nicolas Haller wrote: > On 16/05/2014 09:36, Karl Denninger wrote: >> >> On 5/16/2014 8:23 AM, Nicolas Haller wrote: >>> Hello, >>> >>> I've got a new server and I installed FreeBSD 10 on it. I have a >>> problem to create a new zfs pool. The command stalls on IO wait (D >>> state / zio->io_cv). >>> >>> The device for the pool is a 1.7T partition (index 4) of a gmirror >>> device. >> Why? >> >> ZFS provides its own mirroring and it is superior, as it checksums each >> block and thus does not rely on the drive returning an error to detect >> problems. It can also rewrite a bad block (assuming the problem is >> transient) and scrub also relies on independent components. >> >> You're destroying the data integrity advantage that ZFS gives you by >> using a gmirror under it. Stop doing that and see if your problem >> disappears. >> >> (In other words it sounds like the problem is real but you shouldn't be >> doing that anyway, so it also shouldn't bite you.) >> > > Yes you're right but I have two disks on this server which host my > non-zfs root fs. The first 98G partition you show on "gpart show" > output is my UFS root fs and I want it mirrored. > > As I'm not sure it's a good idea to mix gmirror and ZFS mirror on the > same drives (What do you think about this?), I let gmirror handle the > mirror thing. There are ways to do that (e.g. gmirror a partition or slice; yes, that works) but I wouldn't for several reasons (complexity and the risk of making a mistake in the future that winds up screwing you.) > So, yes, I drop the data integrity advantage, but I keep the > flexibility given by pools/datasets, send/receive, compression... > It's not so bad :-) > Ah, ok, I see what you're doing.... I opted to switch my root partition to zfs and boot from a mirrored ZFS volume. If I'm going to run ZFS *anyway* then I figure I may as well boot from it. There is a potential risk in doing that however -- if something goes wrong with the zfs code you're in deep kimchee. This is most-likely if your emergency boot media is incompatible with a feature flag in the on-disk data set. You have to be CAREFUL doing this to avoid getting nailed; UFS boot is arguably "safer" in that regard, I suppose in that if push comes to shove the individual disks in a gmirror can be mounted since the metadata is confined to the tail end of the drive. -- -- Karl karl@denninger.net [-- Attachment #2 --] 0 *H 01 0 + 0 *H O0K030 *H 01 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1/0- *H customer-service@cudasystems.net0 130824190344Z 180823190344Z0[1 0 UUS10UFlorida10UKarl Denninger1!0 *H karl@denninger.net0"0 *H 0 bi՞] MNԿawx?`)'ҴcWgR@BlWh+ u}ApdCF JVй~FOL }EW^bچYp3K& ׂ(R lxڝ.xz?6 &nsJ +1v9 v/( kqĪp[vjcK%fϻe?iq]z lyzFO'ppdX//Lw(3 JI A*S#՟H[f|CGqJKoo y.oEuOw$ /섀$삻J9b|A P~8]D1YI<"""Y^T2iQ2 b yH)] Ƶ0y$ _N 6XqMC 9 XgώjGTP"#nˋ"Bk1 00 U 0 0 `HB0 U 0, `HB OpenSSL Generated Certificate0 U |8 ˴d[20 U #0]Af4 U3x&^"408 `HB+)https://cudasystems.net:11443/revoked.crl0 *H gBwH] j\x`( &gW32"Uf^. ^Iϱ k!DQA g{(w /)\N'[ oRW @C HO>)XrTNɘ!u`xt5(=f\-l3<@C6mnhv##1ŃbH͍_Nq aʷ?rk$^9TIa!kh,D -ct1 0001 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1/0- *H customer-service@cudasystems.net0 + ;0 *H 1 *H 0 *H 1 140516143412Z0# *H 1y6_ -) 0l *H 1_0]0 `He*0 `He0 *H 0*H 0 *H @0+0 *H (0 +71001 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1/0- *H customer-service@cudasystems.net0 *H 101 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1/0- *H customer-service@cudasystems.net0 *H '4*b$,v'.|J&j/d7<D`V ۮ _R39"kP۲LV\ .-fUjW|5d8U+9:IhsB`9~d_LH4ڽ i<Sj $v֖UtF2*Bt(ITFHмOp ,~B`c"N7l :ѱ'x0 UXhS ngMՊq"ODqPkE #5Gb7j nHsrj&d ecc >1xfm/?f[<.)g%*- S%In$;n 1sz.t8= ȅ߹5PЉ b᳝أv?|30+箱-+ِ~ǃ iNMa5}1DW@/ho8SulT^Wbhome | help
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