Date: Thu, 14 Dec 2017 14:09:39 +0100 From: Daniel Nebdal <dnebdal@gmail.com> To: "O. Hartmann" <ohartmann@walstatt.org> Cc: FreeBSD CURRENT <freebsd-current@freebsd.org> Subject: Re: ZFS RAIDZ1: resilvering at <17.3M/s => abyssal slow ... Message-ID: <CA%2Bt49PJuznLxGnLERwAhVW2CjETJYWO6rKcWo3qOo5bZLQkqYA@mail.gmail.com> In-Reply-To: <20171214124900.64211bd9@thor.intern.walstatt.dynvpn.de> References: <20171214124900.64211bd9@thor.intern.walstatt.dynvpn.de>
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On Thu, Dec 14, 2017 at 12:48 PM, O. Hartmann <ohartmann@walstatt.org> wrot= e: > Hello out there, > > I had to replace a HDD on a RAIDZ1 pool comprised from 4 HDDs, each 3 TB = (netto size of > the pool is about 8-9 TB, the used amount is reported to be ~ 6TB). > > I just started the rebuild/resilvering process and watch the pool crwalin= g at ~ 18 MB/s. > At the moment, there is no load on the array, the host is a IvyBridge XEO= N with 4 core/8 > threads and 3,4 GHz and 16 GB of RAM. The HDDs are attached to a on-board= SATA II (300 > MB/s max) Intel chip - this just for the record. > > Recently, I switch on the "sync" attribute on most of the defined pools's= zfs filesystems > - I also use a SSD for ZIL/L2ARC caching, but it seems to be unused recen= tly in FreeBSD > CURRENT's ZFS - this from a observers perspective only. > > When scrubbing, I see recently also reduced performance on the pool, so I= 'm wondering > about the low throughput at the very moment when resilvering is in progre= ss. > > If the "perspective" of "zpool status" is correct, then I have to wait af= ter two hours > for another 100 hours - ~ 4 days? Ups ... I think there is something badl= y misconfigured > or missing. > > The pool is not "tuned" in any very sophisticated way, since I trust the = kernels ability > to scale automatically - if I'm not wrong for amd64 ... > > Are there any aspects to look at? > > Thanks in advance, > > Oliver > > -- > O. Hartmann > > Ich widerspreche der Nutzung oder =C3=9Cbermittlung meiner Daten f=C3=BCr > Werbezwecke oder f=C3=BCr die Markt- oder Meinungsforschung (=C2=A7 28 Ab= s. 4 BDSG). This is kind of to be expected - for whatever reason, resilvers seem to go super slow at first and then speed up significantly. Just don't ask me how long "at first" is - I'd give it several (more) hours. I don't _think_ sync affects resilver speed (since that's a filesystem level setting and the resilver happens at the block level), but that's pure speculation. The Tuning guide at https://wiki.freebsd.org/ZFSTuningGuide also suggests a list of sysctls you can tweak, which could be worth a try: ### wiki If you're getting horrible performance during a scrub or resilver, the following sysctls can be set: vfs.zfs.scrub_delay=3D0 vfs.zfs.top_maxinflight=3D128 vfs.zfs.resilver_min_time_ms=3D5000 vfs.zfs.resilver_delay=3D0 Setting those sysctls to those values increased my (Shawn Webb's) resilver performance from 7MB/s to 230MB/s. ### --=20 Daniel Nebdal
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