[pve-devel] [PATCH 1/4] RFC: Efficient VM backup for qemu

[Alexandre DERUMIER]

>>1 TB ==> 2MB bitmap 
>>
>>I guess that is small enough. 

Oh yes, no problem !

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

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Mercredi 14 Novembre 2012 05:50:13 
Objet: RE: [pve-devel] [PATCH 1/4] RFC: Efficient VM backup for qemu 


> > Do you keep some blocks maps in memory ? (if yes, what is the memory 
> > usage with big volume?) 
> 
> Yes, we use a bitmap, one bit for one cluster (cluster size = 65536 bytes) 
> 
> 1 TB ==> 16MB bitmap 
> 
> 2^40/2^16 = 2^(40-16) = 2^24 

Oh, just noticed that this is the number of bits (not bytes), so you 
need to divide above result by 8: 

1 TB ==> 2MB bitmap 

I guess that is small enough.