Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Thanks. One more question - is the 2TB limit for a single drbd device, or is that the total for the server? i. On August 30, 2004 07:48 pm, Lars Ellenberg wrote: > / 2004-08-30 16:57:54 -0400 > > \ Ian Samuel: > > Hello, > > > > I tried today to set up DRBD over a software-striped disk set (2 x 1.25 > > TB) for a total DRBD drive of 2.5TB. > > > > Unfortunatley, although the source code for v0.7.2 mentions a maximum > > size of 3.8TB - the size reported back by DRBD as only 310 GB instead. > > > > I can mount and use the /dev/md5 device with reiserfs (I have enabled > > >2TB filesystem support in the kernel), it is only when I try to layer > > DRBD over top that I have a problem with this size of device. > > > > I am using another 50GB drbd parition on the same systems and that works > > fine, and using only 1 disk (1.25GB) also works fine. > > > > Kernel is 2.6.8.1, with DRBD 0.7.2 on Debian sarge. > > Unfortunately I have to admit that we have several pieces in the code > were we still use "unsigned long" as size, sometimes in sectors and > sometimes in kilo byte. > > So the mentioned 3.8 TB are a limit by choice of maximum bitmap size. > the actual limit due to code leftovers from previous times seems to be > much lower. My current tests (and a quick glance at the code) suggest > that you can use up to 1.8TB safely, probably just below 2TB, seemingly > even just below 2.2TB, if meta data is internal (not recommended at that > size because of seektime for meta data updates) and thus the _effective_ > (user visible) size is back at < 2TB ... > > FYI: > > ,--- just seen in my test setup, working: > |drbd0: Creating state block > |drbd0: resync bitmap: bits=503316736 words=15728648 > |drbd0: size = 2013266944 KB > |drbd0: Assuming that all blocks are out of sync (aka FullSync) > |drbd0: 2013266944 KB now marked out-of-sync by on disk bit-map. > > `--- > this is 0x78000400 kb. added an other 0x0800000 kb, > which would end up as 2TB + 1MB, and it just blew up :-( > > Sorry. > We should at least refuse to setup devices of that size until > we sort out these issues. I can even imaging weird OOM conditions or > oopses related to too large devices (if you happen to hit some special > number of sectors ...) > > > Is it unrealistic to use a single DRBD device this large? I am hoping > > it is a simple 32-bit int overflow. > > No, unfortunately it is not that simple. Several unsigned longs need to > be converted to sector_t, some of them to loff_t; several calculations > and far dependencies have to be reviewed, and mached up again. General > code cleanup of leftovers of former times has to follow, and maybe we > need to forcefully break all 2.4. compatibility. > > We'll think it over and let you know. > > Meanwhile, please use devices of less than 2TB to be on the safe side. > > Lars Ellenberg > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user -- Ian Samuel, B.Sc. Sr. Linux System Administrator