On 15 Jul 2010, at 03:16, Todd Lewis wrote: > On 07/14/2010 01:43 PM, Jonathan Nilsson wrote: >> I would like to replicate home directories (and other AFS volumes that >> are primarily accessed read/write) for the purpose of faster disaster >> recovery in certain common cases, such as local hardware failure on an >> AFS File Server. > > Others have offered good advice based on their years of experience that > should be helpful in making this work. By "this" I mean attempting to take > advantage of volume replication in a disaster recovery strategy as a proxy > for high availability. > > My personal opinion here: Don't do this.
I think Todd is perhaps being over cautious here. We (School of Informatics at Edinburgh University) have been running AFS in this configuration ever since we first deployed it in production about 5 years ago. It works very well for us, and we started out as novice AFS users at the start of that deployment process. There are a few important things to consider before you go down this route: *) The problem you are trying to solve. I think you're pretty clear on this, but just to restate. Using read-only replicas is a perfect disaster recovery solution. However, that manual recovery is a human process - you're not going to gain high availability by doing so. *) Promoting a volume from read-only to read-write can require intervention on clients which have recently accessed that volume (running fs checkv) *) You really need management tools to keep all of your various volume copies in check. Our approach is that we have read-write partitions and read-only partitions, so a given read-write partition has a corresponding read-only partition on a geographically remote fileserver. Volume creation, and moves, are done so as to preserve these relationships for all volumes (we also, obviously, have the local r/o to speed up replication) *) You need to consider whether you're going to offer backup volumes too. We use backup volumes to offer a 'yesterday' snapshot functionality, and to support our tape backup system. I think that's all. For what it's worth, the correct functioning of all of this is pretty essential to us, and I'm a pretty active OpenAFS contributor, so it's not likely to break any time soon. Cheers, Simon. _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
