On Jul 23, 2014, at 10:44 AM, Miles Fidelman via illumos-discuss <[email protected]> wrote:
> Richard Elling wrote: >> On Jul 23, 2014, at 4:54 AM, Miles Fidelman via illumos-discuss >> <[email protected]> wrote: >> >>> Looks like AVS, or maybe OHAC, is in the ballpark - but I can't seem to >>> find anything in the way of documentation, status, or anything - other than >>> some old email threads that indicate that both look pretty dead (circa >>> 2011). Sigh.... >> The SNDR portion of AVS does block-level sync and async replication. It is a >> dead >> project because such architectures worked well when disks were 9GB, but suck >> most >> heinously when disks are 4TB. I'll lump DRBD and HAST into that group too. > > Have to say - my experience is otherwise, at least w/ 2TB disks. Granted > rebuilds take time, but that's true with any kind of RAID, but for > synchronous writes to a pair of drives - works just fine. Particularly when > you're only synchronizing selected selected volumes within those drives. >> >> What you will find is that they are easy to setup, easy to fail over to the >> remote site, >> and impractical to return to the original site. > > Actually, it's the setup that's a pain. Failover and recovery work just fine. > > Mind you, I'm not doing multi-site - just multi machine. Avoid the need for > SAN for basic HA of critical VMs. Architecturally, these blind-replication solutions are very susceptible to both the C and P problems in CAP. >> >> As Robert says, the only way to handle multi-site redundancy is to implement >> above >> (application) or below (ZFS). At Coraid, we have the technology to do the >> below: wide-area >> mirroring. Joyent's customers, and many cloud apps, tend to implement above. >> Being >> stuck in the middle is a bad place to be. >> > > Love to do everything at the application level - but that falls down for some > critical applications - notably mail and list processing (which is what our > HA cluster is for). It's a lot easier just to set up a VM on one machine, > with a failover VM on another - replicate the spool directories with DRBD, > and it all just works. I'd love to find a way to do the replication at the > application layer, but so far have yet to find a good model. good luck! -- richard > > For the spool mirroring - without investing in a SAN - DRBD wins big. > There's no other free/cheap solution. Nobody seems to hit the middle market > - small clusters serving small organizations (a department, a lab, small > offices -- a few 1U servers in a rack) - there are LOTs of us in this > segment, but it's not clear there's much money to be made, other than by > commodity hardware vendors. A sweet spot for Supermicro servers - but they > mostly get loaded with open source software. Your stuff is great, but it's > way overkill for us. > > > > > > -- > In theory, there is no difference between theory and practice. > In practice, there is. .... Yogi Berra > > > > ------------------------------------------- > illumos-discuss > Archives: https://www.listbox.com/member/archive/182180/=now > RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175743-23d1427b > Modify Your Subscription: https://www.listbox.com/member/?&; > Powered by Listbox: http://www.listbox.com ------------------------------------------- illumos-discuss Archives: https://www.listbox.com/member/archive/182180/=now RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be Modify Your Subscription: https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4 Powered by Listbox: http://www.listbox.com
