In a previous post i read (Tue Nov 26 18:45:15 CET 2013): - Eric Blevins say: > I have a suggestion that would help alleviate the read and write downsides to > this. > > Create a memory buffer where the reads/writes from the VM are placed. > When buffer is over a certain percentage, stop the backup read operations and > flush the buffer. > The VM can perform IO up to the limit of the memory buffer with little loss in > performance.
- And Dietmar Maurer answers: That is how it works already. Anyways, I will try to upgrade KVM to 1.7 first (many backup related changes). We can then test again and try to optimize further. Then, I say now: ----------------------- The mbuffers for writes can be a serious problem if the PVE Host that have the VM in HA is decomposes during the process of backup, because i will lose data of this VM when this VM starts in the other PVE Node that is alive And my Questions: --------------------------- 1- "KVM live Backup" with the new code of backup, will do write cache for use of the VM? 2- If the question above is correct, how much write cache will make this new code of backup? And the question more important: 3- If the first question is correct, is possible to make a new code of "KVM live Backup" that don't make write cache for use of the VM and nor affect the I/O performance of the VM? Best regrads Cesar ----- Original Message ----- From: "Dietmar Maurer" <diet...@proxmox.com> To: "Cesar Peschiera" <br...@click.com.py>; <pve-devel@pve.proxmox.com> Sent: Tuesday, January 28, 2014 2:52 AM Subject: RE: [pve-devel] KVM Live Backup performance > If is possible without lose performance into this VM, the write cache for "KVM > Live Backup" not must to execute it. In this mode the "KVM Live Backup" will > be > fantastic. Sorry, but I do not really understand that question? We have done many improvement on backup code, so you should first test with the newest binaries available on the 'pvetest' repository.
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