which disk file to choose or which can give me better output

[blason16]

Hi Friends,

I am installing mail server for around 500 users and will be virtualizing on proxmox. Since its a mail servet iops will be higher hence which disk file is suggested? Vmdk or raw or the other one? Also i m choosing kvm 64 bit and using ide as disk type. My server conf is as below

Hp ml 150 g6 with 16 gb ram. 2.13 xeon processor with 4 core and 250 gb sata in rad 1 and 1 TBx 2SATA hardisk in raid 1 again.

I have installed proxmox on 250 gb harddisk and will be using 1 TB disk for images.

Please advise.

 

[mo_]

you get best io-performance with:

type: virtio
format: raw

to enhance IO performance even further, it would be advisable to put the raw "file" as a device instead of an actual file. like... on a SAN

caching is another thing to consider, generally you always use "caching: no" in proxmox for generic VMs, BUT this might be different for low throughput / high io operations/sec applications like mail servers and databases (dont know).

 

[blason16]

I see, now the couple of other things I wanted to know I would be converting .raw to .vmdk just in case for backup purpose. Oh BTW on backup front, I also need to set up backup schedule for the same. Which backup method is more reliable and is that gonna be a Hot Backup or offline/Cold Backup in where I can expect some downtime?

Shall I use LVM snapshot or Suspend? I am looking for hot backup on NFS share. I am also evaluating from faster recovery purporse though I m not planning for Cluster at this moment.

 

[mo_]

I see, now the couple of other things I wanted to know I would be converting .raw to .vmdk just in case for backup purpose.

qemu-img convert (man qemu-img) does all sorts of conversions. even tho the man page says filename1 filename2 as convert parameters, these can also BOTH be devices if you want. "converting" a SAN volume to a raw file or vice versa can simply be done with dd (dd if=/path/to/anything.raw of=/dev/mapper/yourSANvolume bs=50M). be careful with dd tho - you CAN dd vmdk and qcow2 files onto devices and KVM will even accept these and use them. but VMs using this are horribly unstable and VERY likely to just stop dead (found this out after I found something on the internet saying you could simply dd vmdk onto devices...).

Oh BTW on backup front

this would be for someone else to answer for I havent dug into the backup aspect yet