Date: Wed, 12 Apr 2017 13:20:37 -0600 From: Alan Somers <asomers@freebsd.org> To: "Eugene M. Zheganin" <emz@norma.perm.ru> Cc: FreeBSD <freebsd-stable@freebsd.org>, FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: zpool list show nonsense on raidz pools, at least it looks like it for me Message-ID: <CAOtMX2g=xxBBKR6LB0of4tZMddyUJWBTYNFk37Y5kR3rnncMQA@mail.gmail.com> In-Reply-To: <71ef8400-94ec-1f59-3b2b-bb576ad65b89@norma.perm.ru> References: <71ef8400-94ec-1f59-3b2b-bb576ad65b89@norma.perm.ru>
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On Wed, Apr 12, 2017 at 12:01 PM, Eugene M. Zheganin <emz@norma.perm.ru> wrote: > Hi, > > > It's not my first letter where I fail to understand the space usage from zfs > utilities, and in previous ones I was kind of convinced that I just read it > wrong, but not this time I guess. See for yourself: > > > [emz@san01:~]> zpool list data > NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT > data 17,4T 7,72T 9,66T - 46% 44% 1.00x ONLINE - > > > Here' as I understand it, zpool says that less than a half of the pool is > used. As far as I know this is very complicated when it comes to the radiz > pools. Let's see: > > > [emz@san01:~]> zfs list -t all data > NAME USED AVAIL REFER MOUNTPOINT > data 13,3T 186G 27,2K /data > > > So, if we won't investigate further, it looks like that only 186G is free. > Spoiling - this is the real free space amount, because I've just managed to > free 160 gigs of data, and I really know I was short on space when sending > 30 Gb dataset, because zfs was saying "Not enough free space". So, let's > investigate further: > > > [emz@san01:~]> zfs list -t all | more > NAME USED AVAIL REFER MOUNTPOINT > data 13,3T 186G 27,2K /data > data/esx 5,23T 186G 27,2K /data/esx ... > data/esx/boot-esx26 8,25G 194G 12,8K - > data/esx/shared 5,02T 2,59T 2,61T - > data/reference 6,74T 4,17T 2,73T - > data/reference@ver7_214 127M - 2,73T - > data/reference@ver2_739 12,8M - 2,73T - > data/reference@ver2_740 5,80M - 2,73T - > data/reference@ver2_741 4,55M - 2,73T - > data/reference@ver2_742 993K - 2,73T - > data/reference-ver2_739-worker100 1,64G 186G 2,73T - ... > > > This are getting really complicated now. > > What I don't understand is: > > - why the amount of free space changes from dataset to dataset ? I mean they > all share the same free space pool, all have the same refreservation=none, > but the AVAIL differs. When it comes to workerX datasets, it differs > slightly, but when it comes to the large zvols, like esx/shared or > reference, it differs a lot ! > > - why the esx/shared and reference datasets are shown like they can be > enlarged ? I mean, I really don't have THAT much of free space. > > > Here are their properties: > > > [emz@san01:~]> zfs get all data/esx/shared > NAME PROPERTY VALUE SOURCE ... > data/esx/shared refreservation 5,02T local ... > [emz@san01:~]> zfs get all data/reference > NAME PROPERTY VALUE SOURCE ... > data/reference refreservation 3,98T local ... > > > Could please someone explain why they show as having like half of the total > pool space as AVAIL ? I thing this is directly related to the fact that > zpool list shows only 44% of the total pool space is used. And I use this > value to monitor the pool space usage, looks like I'm totally failing with > this. > Some of your datasets have refreservations. That's why. > > I also don't understand whe the zvol of the size 3.97T really uses 6.74T of > the space. I found an article, explaing that the volblocksize and the sector > size has to do something with this, and this happens when the device block > size is 4k, and volblocksize is default, thus 8k. Mine disks sector size is > 512 native, so this is really not the case. I'm also having equal number of > disks in vdevs, and they are 5: > The AVAIL reported by zpool list doesn't account for RAIDZ overhead (or maybe it assumes optimum alignment; I can't remember). But the USED reported by "zfs list" does account for RAIDZ overhead. -alan
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