Date: Tue, 8 May 2001 18:12:11 +0200 From: Gabriel Ambuehl <gabriel_ambuehl@buz.ch> To: freebsd-questions@FreeBSD.ORG Subject: Realtime HD mirroring / network block devices Message-ID: <1431044285272.20010508181211@buz.ch>
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-----BEGIN PGP SIGNED MESSAGE----- Hello, I'm searching for a solution that would allow us to replicate [1] the FS of our servers in realtime or at least close, up to 30 minutes lag are acceptable. Ideally, this could be used with vinum like the Linux crowd does with their network block device but I couldn't find anything similar for FreeBSD and I've never done any Kernel level coding so I doubt this would be a success if I tryed it. Any plans to add such a beast into FreeBSD (http://atrey.karlin.mff.cuni.cz/~pavel/nbd/nbd.html is Linux but BSDL, there is a Winport of the server so I suppose porting it to FreeBSD should possible)? http://www.complang.tuwien.ac.at/reisner/drbd/ is probably exactly what I need but I don't want to run Linux which is too much of a moving target, IMHO. vinum doesn't appear to be supporting any distributed operation at all. vinumvm.org "This isn't too difficult, but it doesn't bring the advantages you might expect: it wouldn't be possible, for example, for different systems to access the closest plex to them, since there would be no way to ensure data consistency." I wouldn't care for this as long as my data is being replicated... I've spent several days trying to get Coda to work but finally came up to the point where I had to say that its architecture isn't really suited for webservers anyway but rather for fileservers providing central homedirs and the like. Available bandwith is at least 100 Mbit, more if needed, so bandwith isn't a problem but CPU resource usage sure is. I don't currently need a setup where multiple machines may change the data as the involved locking headaches would probably eat way more CPU than an additional machine would add, a classical master/slave(s) implementation is enough. In general, I'd be ok with something that just watches for changed files and copies them to the hot standby machine if it only works fast enough without too much impact on system performance. I had a look at both rsync and cpdup but both need way too much CPU resources to scan the drives for changes. I'm not sure whether/how this could be solved. Is there a possibility to have the whole "FAT" (or TOC or whatever, you know what I mean ;-), cached in RAM to save the disk accesses? RAM is cheap nowadays...). The NFSv4 drafts have some sparse information about possible replication of read only filesystems (whatever this may mean. cp -R can do this on read only filesystems.), is any information about the state of NFS4 in general and this very feature in particular available? Best regards, Gabriel [1] No, I don't feel external dual Server RAID is an option. While RAID solves the worry about replicating the data, those devices are still a single point of failure. I won't even think about running a whole group of webservers out of essentially one device which can take them down all at the same time. And pricing is just rip off in the very most cases. Local RAID is fine but still doesn't prevent the data from getting inaccessible when the server crashes. -----BEGIN PGP SIGNATURE----- Version: PGP 6.0.2i iQEVAwUBOvgM18Za2WpymlDxAQGSYwf8DmyVFr2wslbHvwNcf9FDepUgGyS9jGHL uqYiQXEQOjUuLOZx/ioEdbbpUVowCuGa49XDOFvbD0A81Ua92oNbNVcNbvnIXHdI QHddM69wzNrX8aE2mrZRmvSJ+tT1Boc9B6dEIBMu3Or/q3O/Tdd0FPVhU+Jg/RD0 s5xZ3EmlYz4UOR+YmLMCR7DjSQ7uc940csZmHtDOolhv++H2+biOnVJ3yX+/0ONY JkaIs+iAcTz5CzcY0/WfoQT2VABuAe0sLLvnoGJKEumftTgpyiIBvd+uzJlYRI+E 5ThRgqd9Ygys+uDR0FJPU+dIViZi0TbA2mGmKskiGDjug+DifWxgsg== =H8B9 -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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