----- Le 16 Sep 24, à 18:08, G.W. Haywood bac...@jubileegroup.co.uk a écrit :
> Hi there, > > On Mon, 16 Sep 2024, Daniel Berteaud wrote: >> ----- Le 21 Ao? 24, ? 2:02, backu...@kosowsky.org a ?crit : >> >>> First of all, the corruption seems almost definitely to be a disk >>> issue and not a backuppc issue. >> >> I'm just configuring a new BackupPC v4.4 (on Debian, using packages >> from the repo), ... > > Does ZFS work on Linux now? That's a genuine question, not some way > of trying to goad ZFS lovers. ZFS on Linux is rock solid for several years now. >> ... encounter this kind of errors systematically. It's not a >> corruption due to some hardware fault, but clearly a bug in >> BackupPC. > > As I've said before, but I'll repeat, I don't have any BackupPC axe to > grind but Mr. Kosowsky and I both think that what you're seeing looks > like filesystem corruption. And I'm 100% sure it's not. Brand new hardware, reproducible on different (but similar) servers. I've been using ZFS for long enough, and with critical enough workloads to be more confident in it than in BackupPC. > You seem to be of the opinion that this > is not the explanation, and you might be right, but to convince me (at > least) unless I've missed something in your posts which makes the case > conclusively and to which you can point, then I think it must be up to > you to produce that evidence. > >> ... This pool is used for other stuff (1 relatively busy mariadb >> server in a VM, one Proxmox Backup Server storage pool), and >> everything is working correctly. Only BackupPC is having issues. > > The "everything is working correctly" part troubles me. I don't see > that you have evidence for that. The way I approach the logic of > troubleshooting, I'd say you haven't had problems with everything else > *yet*. Well, I cannot make you trust me. Bringing proof that this pool is working doesn't make a lot of sense. I have enough experience in Linux/Sysadmin/ZFS to know this pool is working correctly (stress testing it for several weeks with various workloads), and there's no hardware issue. Nor there's a general ZFS issue. There's still a slight chance it could be a bug in ZFS triggered only by a particular access pattern made by BackupPC. But I wouldn't bet on this. ZFS (even if we count Linux users only) is used by hundred times more users than BackupPC, and is very actively developped (unlike BackupPC), so this pattern would've probably been caught and fixed. But it's a possibility. > And you might never have trouble with anything else, but that > is not the presence of evidence. It is the absence of evidence. > >> Looks like I'm not the only one affected, see >> https://github.com/backuppc/backuppc/issues/494 > > Hmmm. That's on Linux as well - or more strictly, it was in April. > >> I tried 3 times to wipe and start from empty pool, but this comes >> back everytime. So there's a bug in BackupPC. It might only be >> triggered on ZFS (or maybe it's related to the speed on the >> underlying storage, as this one is really the fastest I ever >> used). But there's something. For the first time in more than 18 >> years of using BackupPC, > > I've been running BackupPC for nearly as long as you have, and I've > never seen such errors. But I run ext4. I've managed something like 30 or 40 BackupPC installs with various versions (from 2.1.2 to 4.4.0), using ext3, ext4, xfs. Yes, it was solid (especially in the 3.x era). Since v4, I have a bit less trust in it. And not being able to use ZFS to store backups is painly enough for me to reconsider my backup solution of choice. > > AFAICT so far, the best we can say is that the combination of BackuPC > and ZFS on Linux might be problematic. I can't say I'm surprised, but > I can say that we really don't yet know where your problem lies. Well, the issue is either in BackupPC, or in ZFS. And the probability it's in BackupPC is much (really much) higher. But no, I have no evidence. I just have enough confidence in my storage to be sure the issue only appears with BackupPC. > So > far, I only know of two people running BackupPC on ZFS on Linux. [*] > Both have posted to Github issue 494. Unless there's some lurker here > who's keeping very quiet, in my view as I said above only you and that > other person are in a position in which they will be able to collect > evidence to identify BackupPC as the culprit. Evidence, not anecdote. Well, you ask me to prove my storage pool is working correctly. But I could just as well ask you to prove BackupPC is working correctly. Evidence, not anecdot. I have no doubt BackupPC is working great in most situations (I wouldn't be using it for this long if it wasn't the case). But this issue, which I and a few others are triggering with ZFS is worrying. Because it might not be restricted to ZFS (it could very well just be easier to trigger on ZFS). Nobody wants a backup system which works "most of the time". > > Also I'd say that in a previous post you described a whole lot of what > appeared to me to be completely unnecessary thrashing of storage media > in (something like) the interests of reliability. Not sure which post you're refering to. > My feeling at that > time was that you were making a rod for your own back and I still feel > that way. I kept quiet at the time on grounds of tranquility on this > list, but I believe that you have made things much more complex than > necessary and I'd like to suggest a test... > >> I think I cannot trust my backups anymore. ... very worrying. > > There we can agree. My sugested test is that you fire up a system > using ext4, don't do anything fancy with it, run it in parallel with > your ZFS version, and then sit back and see what happens. And that's what I'll be doing, running BackupPC on XFS, in a VM, on a zvol (because my storage pool is and will stay ZFS, for a lot of different reasons). But I'll loose performance, and some nice features. Anyway, BackupPC seems to become abandonware, so I'll probably migrate to restic sooner rather than later. Regards, Daniel -- Daniel Berteaud _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: https://github.com/backuppc/backuppc/wiki Project: https://backuppc.github.io/backuppc/
