Date: Wed, 02 Aug 2017 14:43:31 +0200 From: "Ronald Klop" <ronald-lists@klop.ws> To: freebsd-fs@freebsd.org, "Eugene M. Zheganin" <emz@norma.perm.ru> Cc: freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: some general zfs tuning (for iSCSI) Message-ID: <op.y4cgaxawkndu52@joepie> In-Reply-To: <8b41e7d6-7a2c-d456-2eee-93efd81aa86a@norma.perm.ru> References: <8b41e7d6-7a2c-d456-2eee-93efd81aa86a@norma.perm.ru>
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On Fri, 28 Jul 2017 12:56:11 +0200, Eugene M. Zheganin <emz@norma.perm.ru> wrote: > Hi, > > > I'm using several FreeBSD zfs installations as the iSCSI production > systems, they basically consist of an LSI HBA, and a JBOD with a bunch > of SSD disks (12-24, Intel, Toshiba or Sandisk (avoid Sandisks btw)). > And I observe a problem very often: gstat shows 20-30% of disk load, but > the system reacts very slowly: cloning a dataset takes 10 seconds, > similar operations aren't lightspeeding too. To my knowledge, until the > disks are 90-100% busy, this shouldn't happen. My systems are equipped > with 32-64 gigs of RAM, and the only tuning I use is limiting the ARC > size (in a very tender manner - at least to 16 gigs) and playing with > TRIM. The number of datasets is high enough - hundreds of clones, dozens > of snapshots, most of teh data ovjects are zvols. Pools aren't > overfilled, most are filled up to 60-70% (no questions about low space > pools, but even in this case the situation is clearer - %busy goes up in > the sky). > > So, my question is - is there some obvious zfs tuning not mentioned in > the Handbook ? On the other side - handbook isn't much clear on how to > tune zfs, it's written mostly in the manner of "these are sysctl iods > you can play with". Of course I have seen several ZFS tuning guides. > Like Opensolaris one, but they are mostly file- and > application-specific. Is there some special approach to tune ZFS in the > environment with loads of disks ? I don't know.... like tuning the vdev > cache or something simllar. ? > > > Thanks. > > Eugene. What version of FreeBSD are you running? What is the system doing during all this? How are your pools setup (raidz1/2/3, mirror, 3mirror)? How is your iSCSI configured and what are the clients doing with it? Is the data distributed evenly on all disks? Do the clients write a lot of sync data? I think this kind of information helps people helping you. Regards, Ronald.
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