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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