Date: Wed, 29 Sep 2010 10:02:43 -0700 From: Aaron <drizzt321@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: Disappearing available space with ZFS...what am I missing? Message-ID: <AANLkTin%2B4-qWeBJsX%2B_2MPyhojvWc8w3dP9y7znTFdLv@mail.gmail.com> In-Reply-To: <AANLkTinN0dDZve0Dk3S6CTAkAwa_G3jqPzhedO%2BRRTVq@mail.gmail.com> References: <AANLkTinRWacA8%2BYjy91S_P==o2QZbc4nmqweXiEyHm9L@mail.gmail.com> <4CA302E5.9050004@pp.dyndns.biz> <AANLkTinN0dDZve0Dk3S6CTAkAwa_G3jqPzhedO%2BRRTVq@mail.gmail.com>
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On Wed, Sep 29, 2010 at 03:14, krad <kraduk@gmail.com> wrote: > > > On 29 September 2010 10:12, Morgan Wesström > <freebsd-questions@pp.dyndns.biz> wrote: >> >> On 2010-09-29 07:56, Aaron wrote: >>> >>> I've created a ZFS pool with zpool create tank raidz ada0 ada1 ada2 >>> ada3, and then I add some additional mountpoints (I think they're >>> called) using zfs create tank/storage, etc. In zpool list, I see the >>> pool with 3.62T available. With df -h, I see 2.4T available for tank, >>> and tank/storage. When I first created tank, it had the 3.62T >>> available as I expected. What am I missing? I do have compression set >>> to gzip-9 on tank which gets inherited like I want, don't know if that >>> would affect anything. >>> >>> --Aaron >> >> There's nothing wrong here that I can see, you just have to make a >> distinction between the zfs pool and the filesystems within the pool and I >> agree it can be confusing at first. >> >> The numbers suggest you are using 4 x 1TB (base 10 TB) drives? That equals >> 3.7TiB (base 2 TB) which is the unit zpool/zfs uses. This is the total >> amount of space available to the pool and includes all space on all drives >> in the pool. Nothing strange so far. >> >> Now, since you've told zpool to create filesystems within the pool using >> raidz, the filesystems will have 25% less space available since this space >> is used for parity data. So a filesystem using the whole pool will report >> having 3.7 * 0.75 = 2.7TiB available which is in agreement with your >> numbers. A raidz filesystem will always lose 1 disk worth of space and will >> never report that space as available to you since it will always be occupied >> with parity data. >> >> The pool on the other hand doesn't make a distinction, in this case >> anyway, between user data and parity data so zpool will always report what's >> actually unallocated on all your physical drives in the pool. For every GiB >> you allocate in the filesystem you will allocate 1.33GiB in the pool since >> that includes parity data. "zfs list" and "df -h" are your best friends to >> find out how much space is available for your files. Don't bother about >> "zpool list". >> >> Regards >> Morgan >> _______________________________________________ >> freebsd-questions@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-questions >> To unsubscribe, send any mail to >> "freebsd-questions-unsubscribe@freebsd.org" > > > It gets even more hairy when you start adding in reservsions, quotas, and > compression. Slap dedup on top of that and you get magically growing fs > according to df 8) > > Ahhh...yea. Thanks everyone! I didn't realize that zpool status would show the raw space (so 4x1TB base10 is ~3.7TB base2), and not the available space after the 4-1 RAIDZ usage consumes. So that all makes sense, as well as with reservations, quotas and compression now causing df to not really know what's going on. If I want to get the actual values of available space vs used space, I should use zfs get all <filesystem> and look at the properties there? --Aaron
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