Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2005-08-06 18:49:00 -0400 \ Maurice Volaski: > Our internal 3ware RAID did something bad and the logs starting > filling with scary errors: > > Jul 31 03:10:15 [kernel] [1745925.523238] PCI-DMA: Out of IOMMU space for 16384 bytes at device 0000:03:01.0 > Jul 31 03:10:15 [kernel] [1745925.524623] SCSI error : <0 0 0 0> return code = 0x70000 > Jul 31 03:10:15 [kernel] [1745925.524626] end_request: I/O error, dev sda, sector 47586099 > > (I have changed the IOMMU allocation from 32 MB to 512 MB to address the issue, I hope) > > One of the affected partitions is under drbd, but the rest is the > root. Something somewhere made the root partition read-only. And it > did so to the drbd partition too, but oddly nobody seems to be > complaining they can't access the database on it. > So if I understand this correctly: > > 1) drbd is a true mirrored RAID for both writing AND reading. yes of course :) only that reads are always local, as long as there is something (good) local, and that you can configure "on-io-error panic;" (default is detach, iirc), in which case the node in question should have committed suicide, and the other had taken over. > 2) I don't want to necessarily configure the OS or drbd to > automatically kill the primary should the RAID start to fail. drbd > will just use the secondary so long as the primary's OS and network > are intact. _and_ the internal link stays up. so you still should failover as soon as possible and convenient. this is intended to allow for a graceful failover after local io error (be nice to your services, choose a suitable point in time for your users). > This fantastic feature ought to be noted in the documentation a bit > more explicitly. I previously thought of drbd only in terms of the > primary's failing globally requiring heartbeat intervention to produce > a failover. [ we are good? sure we are good. we know that. so why should we run about talking big? ] -- : Lars Ellenberg Tel +43-1-8178292-0 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Schoenbrunner Str. 244, A-1120 Vienna/Europe http://www.linbit.com : __ please use the "List-Reply" function of your email client.