Indeed if we have two RO replicas at Site B and RW at site A, subsequent release will be twice as consuming, unless "vos release" can be made to be even smarter, such that data is "relayed" among RO sites instead of being broadcasted from the RW site.
I guess that touches some fundamental part of "vos release" which is not trivial: How to optimize the data propagation path for different network scenarios? How does that affect the integrity among different replicas? Thank you both for the practical advice. Best regards, Ximeng (Simon) Guan -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Todd Lewis Sent: Monday, August 6, 2018 5:45 AM To: [email protected] Subject: Re: [OpenAFS] Does vos release/volume replication always initiates data transfer from RW site? Given the two-site scenario below, and successful manual replication as outlined by Jeffrey further below, you then have two RO volumes at site B as desired. If "vos release" is enough of a problem to warrant this manual intervention, then won't subsequent releases from the RW site A now be twice as consuming, and therefore justify (?) removal of the 2nd replica prior to a release, then the release, followed by a repeat of the dump/restore/addsite process to recreate the 2nd replica? This can be scripted, but it's a balance between the extra work for the admin vs for the machines/network. -- Todd Lewis On 08/06/2018 08:28 AM, Jeffrey Altman wrote: > On 8/5/2018 11:58 PM, Ximeng Guan wrote: >> Hello, >> >> We have one cell covering two sites. The WAN bandwidth between the >> two sites is relatively low, so we use volume replication to speed up >> the access. >> >> Those replicated volumes are often large in size. So replication to >> the remote site is an operation whose cost cannot be neglected. >> >> Now with RW volumes at site A and their RO replication on servers at >> site B, we want to bring up a new file server at site B to balance >> the load. In other words we would like to “offload” a majority of the >> RO volumes from one server to a different server at Site B, without >> touching their RW masters at Site A. >> >> [...]> >> I wonder if there is a way to directly transfer those RO volumes btw >> servers at site B, without breaking the data integrity among the RO >> sites or affecting the atomicity of “vos release”. > AuriStorFS supports the desired functionality including the ability to > copy and move readonly sites between file servers or vice partitions > attached to the same file server. > > https://www.auristor.com/openafs/migrate-to-auristor/ > > OpenAFS does not contain explicit functionality but it is possible > using > > vos dump > vos restore -id -readonly > vos addsite -valid > > to achieve similar results. From the source server use "vos dump" to > generate a dump stream of the readonly volume you wish to replicate. > Pipe the output to "vos restore" specifying the destination server, > partition, the readonly volume id and the -readonly flag to specify > the volume type. Finally, use "vos addsite" with the -valid flag to > update the location service entry for the volume. The -valid flag > indicates that the readonly volume data is known to be present and > consistent with other sites. Note that the -valid switch will not mark a > site as "new" > if a "vos release" failed to update one or more sites. > > Be careful to use publicly visible addresses when executing these commands. > > Jeffrey Altman _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
