[pve-devel] KVM Live Backup performance

[Cesar Peschiera]

Thanks Alexander for your answers (You are the Master of Masters), but the 
questions are based in the buffer read/write of "KVM Live Backup"
In the company exist a person hired as DBA of MS-SQL Server, then my 
preocupation is only about of behavior of this VM while "KVM Live Backup" is 
running and not of the memory for MS-SQL Server.

Please, Can you send me the answers again?

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 with a 
NIC of 1 Gb/s, and i don't want get performance degradation or at least a 
minimun of degradation while "KVM Live Backup" is running

And the fifth question:
What will happen if this NFS Server suddenly decomposes while "KVM Live 
Backup" is running?

Best regards
Cesar

----- Original Message ----- 
From: "Alexandre DERUMIER" <aderumier at odiso.com>
To: "Cesar Peschiera" <brain at click.com.py>
Cc: <pve-devel at pve.proxmox.com>
Sent: Wednesday, January 29, 2014 12:38 AM
Subject: Re: [pve-devel] KVM Live Backup performance


>>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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