[pve-devel] KVM Live Backup performance

[Alexandre DERUMIER]

>>1- But as the buffer need RAM free, what are the RAM requirements for use this buffer? 

Do you mean buffer for your sqlserver in windows guest ?

if yes, it's like a real server : enough ram to handle all the database in memory  ;)


>>2- The requeriments of buffer RAM will be always static in any case, or will be dinamic? 

The memory is dynamic between different vms, if the vms don't use it.
But if you are using a database, it should use all the memory available in the guest. (or you need to limit maxmemory usage it in sqlserver)

----- Mail original -----

De: "Cesar Peschiera" <brain at click.com.py> 
À: pve-devel at pve.proxmox.com 
Envoyé: Mardi 28 Janvier 2014 19:14:22 
Objet: Re: [pve-devel] KVM Live Backup performance 


Thanks for your nice answer Eric 

@Dietmar or anyone that can answer, please let me to do a questions: 

Note: 
These questions is because I am involved in a project and the idea is to use several RAID 10 in the same PVE Host for use of a VM with MS-SQL Server, and for the backup a single SATA hard drive will be used on an NFS Server, and i don't want get performance degradation or at least a minimun of degradation 

1- But as the buffer need RAM free, what are the RAM requirements for use this buffer? 
2- The requeriments of buffer RAM will be always static in any case, or will be dinamic? 
3- If is dinamic, which will be the formula that i need to know for obtain a nice performance? (for buy the RAM that will be necessary) 
4- Will get I at least a minimum of degradation in this case ( obviously while "KVM Live Backup" is running) ? (see the note above) 

Best regards 
Cesar 


----- Original Message ----- 
From: Eric Blevins 
To: pve-devel at pve.proxmox.com 
Sent: Tuesday, January 28, 2014 11:12 AM 
Subject: Re: [pve-devel] KVM Live Backup performance 




<blockquote>


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. 



Cesar, from my testing KVM 1.7 fixed the backup related performance issues. 
See archive: http://pve.proxmox.com/pipermail/pve-devel/2013-December/009296.html 

The buffers related to Live backup are for the data sent to the backup, not the data sent to the VMs disk. 
The data sent to the disk will still use whatever cache policy you have set for that disk. 



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</blockquote>

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