Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> -----Original Message----- > From: drbd-user-bounces at lists.linbit.com > [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Lars > Ellenberg > Sent: Thursday, January 11, 2007 8:22 AM > To: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] Use DRBD and LVM Snapshots to create > a point-in-timereplica > > / 2007-01-11 12:29:11 +0100 > \ Ralf Schenk: > > Ross S. W. Walker schrieb: > > > As the subject says I want to know if it is possible to > use DRBD and LVM > > > snapshots to create a point-in-time replica? > > > > > > This would allow me to rotate snapshots in a pattern that > would provide > > > the best consistency/coverage for my needs. > > > > > > > Hello ! > > > > I do this on a server pair with DRBD 8.0pre6 under XEN. I > think you will > > have to use DRBD 8.X because only later DRBD Versions claim to run > > without problems on top of LVM Volumes. > > drbd 0.7 is also fine on top of lvm > (thats our typical setup: md - lvm - drbd) > or below lvm (as pv) > or even (if you really want to have a headache) in some weird > lower lv as storage of drbd as pv for some upper vg setup. > > > I snapshot the underlying LVM Volumes readonly and do rsync style > > rotating Backups with the help of dirvish (http://www.dirvish.org/). > > you probably should snapshot them rw, so the file system is able to > replay its journal. you obviously should mount them ro, of course. > > > To have consistent backups of my MySQL Databases I have a > small perl-skript > > that runs before the backup which commits a "FLUSH TABLES WITH READ > > LOCK" to the MySQL Database. After the skript has taken the > LVM Snapshot > > via "system" calls I do "UNLOCK TABLES" so the tables are unlocked. > > right. so you know that at least the the mysql tables are consistent > in the snapshot. > > > Usually this takes about 1-3 seconds and sessions that > attempt to write > > to MySQL wait longer for response so that only a short lock > can be detected. > Sounds interesting, but I am hoping to take things 1 step further. The drbd volumes will be exported via iSCSI to Windows hosts that will be running Exchange, SQL server and MS Virtual Server off them. I currently do not have a reliable way to put these volumes into a consistent state before snapshotting them, so I am leaning towards using drbd for Exchange and Virtual Machines full time using Prot A (asynchronous), and using the SQL Server Log Shipping to keep backup databases current. The replicas will be geographically disperse linked together over a single T1 line. It's the T1 line that I am unsure about and will most likely be the weakest link in this. -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.