Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Am Dienstag, 1. Februar 2011, um 16:49:05 schrieb Ivan Frain: > Hi all, > > I am currently evaluating DRBD as a storage candidate for highly > available storage in a virtualized environment. > It seems like a very good alternative to expensive SAN/NAS. > I was wondering how DRBD deals with the network block device deadlock > problem. > This problem (described here: http://lwn.net/Articles/195416/) can be > summarized as follows: if the system runs short in memory, it will try > to write dirty page to disk in order to free memory space. if the > disk is a network block device, the dirty page write may need to > allocate some other memory pages which is not possible since the > solution to have more memory available was to write the dirty page to > disk. > This is a very well understood issue. The solution to the issue is, that all memory allocations in the write out path are backed by mempools (= Small amounts of pre allocated memory). DRBD does not deadlock in out of memory situations, at least since version 8. Maybe even earlier. Best, Phil -- : Dipl-Ing Philipp Reisner : LINBIT | Your Way to High Availability : Tel: +43-1-8178292-50, Fax: +43-1-8178292-82 : http://www.linbit.com DRBD(R) and LINBIT(R) are registered trademarks of LINBIT, Austria.