-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 You didn't specify your database, but if you are using mysql you can use: [mysqld] # Change disk flush to every second instead of after each transaction. innodb_flush_log_at_trx_commit=2 to specify flushing the logs every X seconds instead of after every transaction. It really depends if you can afford to lose any transactions. This helped on a machine that had some high disk waits and were I felt comfortable enough losing two seconds of transactions. In my situation it took an almost 30 minute query to ~30 seconds. Now that the disk issue is resolved, I don't use that option any more. -----BEGIN PGP SIGNATURE----- Version: Mailvelope v1.0.0 Comment: https://www.mailvelope.com wsFcBAEBCAAQBQJV1OtLCRDmVDuy+mK58QAA420QAJmjJvK4fvoYJb5eNKDg z1cxO4+v3ue+cFX6cj8HnO5ByYKWCroxfTHU159b3L2LvGQVkJso7ogR6e82 rkcDeaLYs82TupBcszCnMpCcI6NB7PrWMp8LPkhiqnitd+tVntZQ+bHSPPGQ vGSp1b8WC9AwjnkiifX6jNhS9KxbKPrzqlfQfGcxEaC082lWp2E+MInDWYct K1tYiCfVrvNWVa5JWwU5xXDasHJNeA9Xam4h1Bvy3m3coueF7hVL2k3sV9d0 OkcfQbyNVeOxViQ4FbfT1RdgtWO9UdkNoj7ujtGaK6nPN2icLNnuVQqw+gq0 F2FTBDDAz9C/pSiYeljyKE5QoU0iDJNtadbnlgg8zqZC8o1F5TVrUIv4a6Hz +Vr+KQ/MY2QK6qXSRxDrR6MBQqMkC7jDC05/bx1CI5dgPEtetN6LXIO6fk30 8Y6PRCMIr0/dvseBFkO8rdASFf3aLDvVPuQMnyWwrMhFzzsxDfP/mWrOby3K WXD2hvRuXltLe3XwuAocZVXSSIgTQnBCfe9HeKnbR6p+4LZjxUfq/EaEg56F 9swbl33e4NByk/te63KuwDs7o+CWzzD3LOBkSXyolWKWsH6uSiklwGOSiYO8 xqgIbN9Lwzo//T14DyZfZRExfRhLgC99eGqpLdROs2P/i+1E9O8pRMr7i/Ls Huga =Ef88 -----END PGP SIGNATURE----- ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1 On Wed, Aug 19, 2015 at 8:20 AM, Logan Barfield <lbarfield@xxxxxxxxxxxxx> wrote: > Hi, > > We are currently using 2 OSD hosts with SSDs to provide RBD backed volumes > for KVM hypervisors. This 'cluster' is currently set up in 'Location A'. > > We are looking to move our hypervisors/VMs over to a new location, and will > have a 1Gbit link between the two datacenters. We can run Layer 2 over the > link, and it should have ~10ms of latency. Call the new datacenter > 'Location B'. > > One proposed solution for the migration is to set up new RBD hosts in the > new location, set up a new pool, and move the VM volumes to it. > > The potential issue with this solution is that we can end up in a scenario > where the VM is running on a hypervisor in 'Location A', but writing/reading > to a volume in 'Location B'. > > My question is: what kind of performance impact should we expect when > reading/writing over a link with ~10ms of latency? Will it bring I/O > intensive operations (like databases) to a halt, or will it be 'tolerable' > for a short period (a few days). Most of the VMs are running database > backed e-commerce sites. > > My expectation is that 10ms for every I/O operation will cause a significant > impact, but we wanted to verify that before ruling it out as a solution. We > will also be doing some internal testing of course. > > > I appreciate any feedback the community has. > > - Logan > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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