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Hi Matevz, It is XrdOssCache::Alloc() and I will gaurantee you that it will not choose a full disk if it has properly confiurted. The default is proper so I don't know if there have been any overrides here. Andy On Mon, 27 Feb 2023, Matevz Tadel wrote: > Hi Nikolai, > > I don't think this matters, xcache uses last file access time as written in the > cinfo file. > > I still suspect something goes wrong with the disk selection for placement of > new files -- the full disk should simply not be chosen over the other disks and > thus stop filling up. > > Wiping the whole cache would help, at least for a while :) ... but it would be > good to understand what is going on here. Would you be able to run with a custom > build? Potentially we could just replace a single library to include some printouts. > > Andy, remind me please ... where is the code that does disk selection? Is it > XrdOssCache::Alloc()? > > Cheers, > Matevz > > On 2/16/23 02:27, Nikolai Hartmann wrote: >> Hi again, >> >> Actually it seems to only change the "change" time (st_ctime) >> >> touch test >> stat test >> [...] >> Access: 2023-02-16 11:25:11.962804882 +0100 >> Modify: 2023-02-16 11:25:11.962804882 +0100 >> Change: 2023-02-16 11:25:11.962804882 +0100 >> Birth: 2023-02-16 11:25:11.962804882 +0100 >> >> chown xrootd test >> stat test >> [...] >> Access: 2023-02-16 11:25:11.962804882 +0100 >> Modify: 2023-02-16 11:25:11.962804882 +0100 >> Change: 2023-02-16 11:25:20.322843125 +0100 >> Birth: 2023-02-16 11:25:11.962804882 +0100 >> >> Does this play a role? >> >> Cheers, >> Nikolai >> >> On 2/16/23 11:18, Nikolai Hartmann wrote: >>> Hi Matevz (including xrootd list again which i forgot in the last reply), >>> >>>> Well, if for some reason more new files are placed on a single disk, >>>> those files will be "newer" and purge would preferentially wipe data >>>> off other disks. >>> Mhhhh - then i have an idea how i may have triggered this. As mentioned in my >>> first email the issue started after i updated my container image and had to >>> change the xrootd user ids. This changes the Access time of the files - if >>> that is used by xrootd to determine which files are newer than it could just >>> be that the chown process walked this directory last and therefore will purge >>> it last. >>> When i then deleted it when the disk ran full i made the problem even worse >>> since now all the files that end up there are recently accessed. >>> >>> So deleting the whole cache should fix it? >>> >>> Cheers, >>> Nikolai >>> >>> On 2/16/23 10:50, Matevz Tadel wrote: >>>> Hi Andy, Nikolai, >>>> >>>> On 2/15/23 23:51, Andrew Hanushevsky wrote: >>>>> Hi Nikolai, >>>>> >>>>> Hmm, this sounds like an off by one problem in Xcache. >>>> >>>> How? XCache does not do disks, it just uses oss API to a pool. >>>> >>>>> The question is what is >>>>> the "one". It does seem that ity consistently does not purge files from a >>>>> particular disk but then again it doesn't know about disks. So, there is some >>>>> systematic issue that resolves to ignoring a disk. Matevz? >>>> >>>> Well, if for some reason more new files are placed on a single disk, those files >>>> will be "newer" and purge would preferentially wipe data off other disks. >>>> >>>> That's why I asked in the first email how disks are selected for new files and >>>> if we could inject some debug printouts there. >>>> >>>> Perhaps a coincidence, but the full disk is the one that is listed first by df. >>>> >>>> The docs say default for oss.alloc fuzz = 0 and that this "forces oss to always >>>> use the partition with the largest amount of free space" -- so the fuller one >>>> should never get selected for new files. And xcache does pass the appropriate >>>> oss.asize opaque parameter to open. >>>> >>>> https://urldefense.com/v3/__https://xrootd.slac.stanford.edu/doc/dev56/ofs_config.htm*_Toc116508676__;Iw!!Mih3wA!CPJXm6eN-2_hoD2H_DidLrJJIwTvYUTK7V8pRT64GhSwBlmFYugKLfTk2O6zoR2otc1TQNvfczttg_nl$ >>>> Matevz >>>> >>>>> Andy >>>>> >>>>> >>>>> On Thu, 16 Feb 2023, Nikolai Hartmann wrote: >>>>> >>>>>> Hi Andy, >>>>>> >>>>>> The behavior seems to be that it purges all the disks except one. After the >>>>>> other disks now again surpassed the threshold of 95% it seemed to trigger the >>>>>> cleanup and now i have this: >>>>>> >>>>>> Filesystem Type Size Used Avail Use% Mounted on >>>>>> /dev/sdb btrfs 5,5T 5,3T 215G 97% /srv/xcache/b >>>>>> /dev/sda btrfs 5,5T 5,0T 560G 90% /srv/xcache/a >>>>>> /dev/sdh btrfs 5,5T 4,9T 588G 90% /srv/xcache/h >>>>>> /dev/sdj btrfs 5,5T 4,9T 584G 90% /srv/xcache/j >>>>>> /dev/sdf btrfs 5,5T 4,9T 580G 90% /srv/xcache/f >>>>>> /dev/sdm btrfs 5,5T 5,0T 535G 91% /srv/xcache/m >>>>>> /dev/sdc btrfs 5,5T 5,0T 553G 91% /srv/xcache/c >>>>>> /dev/sdg btrfs 5,5T 4,9T 612G 90% /srv/xcache/g >>>>>> /dev/sdi btrfs 5,5T 4,9T 596G 90% /srv/xcache/i >>>>>> /dev/sdl btrfs 5,5T 5,0T 518G 91% /srv/xcache/l >>>>>> /dev/sdn btrfs 5,5T 4,9T 570G 90% /srv/xcache/n >>>>>> /dev/sde btrfs 5,5T 4,9T 593G 90% /srv/xcache/e >>>>>> /dev/sdk btrfs 5,5T 4,8T 677G 88% /srv/xcache/k >>>>>> /dev/sdd btrfs 5,5T 4,9T 602G 90% /srv/xcache/d >>>>>> >>>>>> Cheers, >>>>>> Nikolai >>>>>> >>>>>> On 2/14/23 21:52, Andrew Hanushevsky wrote: >>>>>>> Hi Matevz & Nikolai, >>>>>>> >>>>>>> The allocation should favor the disk with the most free space unless it's >>>>>>> atered using the oss.alloc directive: >>>>>>> https://urldefense.com/v3/__https://xrootd.slac.stanford.edu/doc/dev54/ofs_config.htm*_Toc89982400__;Iw!!Mih3wA!AsisYxoXis_6IdoiqK-BwdMsHfHTB41Z4-GEjaMqvO0PQHh6TqU8Sn79JUgDeJDLCvO63yQiG63Zu6syVA$ >>>>>>> I don't think Nikolai specifies that and I don't think the pfc alters it in >>>>>>> any way. So, I can't explain why we see that difference other than via an >>>>>>> uneven purge. >>>>>>> >>>>>>> Andy >>>>>>> >>>>>>> >>>>>>> On Tue, 14 Feb 2023, Matevz Tadel wrote: >>>>>>> >>>>>>>> Hi Nikolai, Andy, >>>>>>>> >>>>>>>> I saw this a long time back, 2++ years. The thing is that xcache does oss >>>>>>>> df on >>>>>>>> the whole space and then deletes files without any knowledge of the usage on >>>>>>>> individual disks themselves. Placement of new files should prefer the more >>>>>>>> empty >>>>>>>> disks though, iirc. >>>>>>>> >>>>>>>> I remember asking Andy about how xcache could be made aware of individual >>>>>>>> disks >>>>>>>> and he prepared something for me but it got really complicated when I was >>>>>>>> trying >>>>>>>> to include this into the cache purge algorithm so I think I dropped this. >>>>>>>> >>>>>>>> Andy, could we sneak some debug printouts into oss new file disk >>>>>>>> selection to >>>>>>>> see if something is going wrong there? >>>>>>>> >>>>>>>> Nikolai, how fast does this happen? Is it a matter of days, ie, over many >>>>>>>> purge >>>>>>>> cycles? Is it always the same disk? >>>>>>>> >>>>>>>> Cheers, >>>>>>>> Matevz >>>>>>>> >>>>>>>> On 2/13/23 23:21, Nikolai Hartmann wrote: >>>>>>>>> Hi Andy, >>>>>>>>> >>>>>>>>> The config is the following: >>>>>>>>> >>>>>>>>> https://urldefense.com/v3/__https://gitlab.physik.uni-muenchen.de/etp-computing/xcache-nspawn-lrz/-/blob/086e5ade5d27fc7d5ef59448c955523e453c091f/etc/xrootd/xcache.cfg__;!!Mih3wA!DfZZQn5-SZKaGYvPW97K8SD5gDYYTy0wuUgMgQCUMhwQehl01yhKQdErjCRUz3BoZYL_nKVipwRIRYyR$ >>>>>>>>> The directories for `oss.localroot` and `oss.space meta` are on the system >>>>>>>>> disk. >>>>>>>>> The `/srv/xcache/[a-m]` are individually mounted devices. >>>>>>>>> >>>>>>>>> Best, >>>>>>>>> Nikolai >>>>>>>>> >>>>>>>>> On 2/14/23 00:34, Andrew Hanushevsky wrote: >>>>>>>>>> Hi Nikolai, >>>>>>>>>> >>>>>>>>>> Hmmm, no it seems you are the first one. Then again, not many people >>>>>>>>>> have a >>>>>>>>>> multi-disk setup. So, could you send a link to your config file? It >>>>>>>>>> might be >>>>>>>>>> the case that all of the metadata files wind up on the same disk and >>>>>>>>>> that is >>>>>>>>>> the source of the issue here. >>>>>>>>>> >>>>>>>>>> Andy >>>>>>>>>> >>>>>>>>>> On Mon, 13 Feb 2023, Nikolai Hartmann wrote: >>>>>>>>>> >>>>>>>>>>> Dear xrootd-l, >>>>>>>>>>> >>>>>>>>>>> I'm seeing the issue that one of the disks on one of our xcache servers >>>>>>>>>>> fills >>>>>>>>>>> up disproportionally - that means it runs completely full until i get "no >>>>>>>>>>> space left on device" errors without xcache running cleanup, while the >>>>>>>>>>> other >>>>>>>>>>> disks still have plenty of space left. My current df output: >>>>>>>>>>> >>>>>>>>>>> /dev/sdb btrfs 5,5T 5,2T 273G 96% /srv/xcache/b >>>>>>>>>>> /dev/sda btrfs 5,5T 4,9T 584G 90% /srv/xcache/a >>>>>>>>>>> /dev/sdh btrfs 5,5T 5,0T 562G 90% /srv/xcache/h >>>>>>>>>>> /dev/sdj btrfs 5,5T 5,0T 551G 91% /srv/xcache/j >>>>>>>>>>> /dev/sdf btrfs 5,5T 4,9T 579G 90% /srv/xcache/f >>>>>>>>>>> [...] >>>>>>>>>>> >>>>>>>>>>> If you look at the first line you see that disk is 96% full while the >>>>>>>>>>> others >>>>>>>>>>> are around 90%. The issue occurred the first time after i built a new >>>>>>>>>>> container for running xrootd. That change involved switching the >>>>>>>>>>> container >>>>>>>>>>> from centos7 to almalinux8 and changing the xrootd user id (ran chown and >>>>>>>>>>> chgrp afterwards on the cache directories which are bind mounted). The >>>>>>>>>>> xrootd >>>>>>>>>>> version stayed the same (5.4.2). The high/low watermark configuration >>>>>>>>>>> is the >>>>>>>>>>> following: >>>>>>>>>>> >>>>>>>>>>> pfc.diskusage 0.90 0.95 >>>>>>>>>>> >>>>>>>>>>> I already tried clearing the misbehaving disk (after it ran full to >>>>>>>>>>> 100%), >>>>>>>>>>> but now the issue is reappearing. Has anyone seen similar issues or >>>>>>>>>>> does it >>>>>>>>>>> ring any bells for you? >>>>>>>>>>> >>>>>>>>>>> One thing i checked is the size that xrootd reports in the log for the >>>>>>>>>>> total >>>>>>>>>>> storage and that at least matches what i get when i sum the entries from >>>>>>>>>>> `df`. >>>>>>>>>>> >>>>>>>>>>> Cheers, >>>>>>>>>>> Nikolai >>>>>>>>>>> >>>>>>>>>>> ######################################################################## >>>>>>>>>>> Use REPLY-ALL to reply to list >>>>>>>>>>> >>>>>>>>>>> To unsubscribe from the XROOTD-L list, click the following link: >>>>>>>>>>> https://urldefense.com/v3/__https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=XROOTD-L&A=1__;!!Mih3wA!DfZZQn5-SZKaGYvPW97K8SD5gDYYTy0wuUgMgQCUMhwQehl01yhKQdErjCRUz3BoZYL_nKVip_SnON6x$ >>>>>>>> >>>>>> >>>> > ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the XROOTD-L list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=XROOTD-L&A=1