How much load the backup process put on Host & SAN?

[curiousagain]

Hi,

I have 2 hosts and 2 SANs, one SAN old all the VM's and the other one hold all the backups and in case of SAN failure it will switch the first SAN.

I would like to take a backup twice a day, once at night and once during the day (~14:00 PM).

My question is, how much load the backup process put on the host and on the SAN with LIVE system?

is it something that I can "live" with it?

thanks.

[AndreTheGiant]

It depends by your SAN performance and by your transport mode during backup.

Usually SAN is not affected (the only issues that I see was with slow disk, like SATA).

But you must use a SAN transport (for example with VCB) cause network transport could affect your network performance too much.

Or you have to consider differential/Incremental mode... in this case you reduce both the "load" of the backup and also the backup time.

Andre

[curiousagain]

thanks for your prompt reply.

I'm using the VCB script on the free ESXi, does it transfer all the data directly from the SAN to the Backup server without using the host?

What is the difference between SAN transport & Network Transport?

Does the incremental mode switch files that were changed or write them again and the backup file is getting bigger and bigger for each backup?

Thanks.

[AndreTheGiant]

I'm using the VCB script on the free ESXi, does it transfer all the data directly from the SAN to the Backup server without using the host?

Which scripts?

What is the difference between SAN transport & Network Transport?

In official VCB (not avaible with free products) you have different way to make the backup transfert: or using network (like usual backup program) or using SAN (in this case you VCB proxy will save data directly from the SAN and not from the VM or the ESX).

Does the incremental mode switch files that were changed or write them again and the backup file is getting bigger and bigger for each backup?

Incremental save all changed data from the last backup.

Differential save all changed data from the last full backup.

So differential will alway groove (but you need only 2 file for the restore). Incremental could have different size each days (but your need all incremental files).

PS: your can do differential or incremental ONLY if your backup program or framework will support this methods. Same for different transport mode.

Andre

[curiousagain]

I'm using the "ghettoVCB4i.sh" script for backup, are you familiar with it?

if yes, does it have Differential backup capabilities?

[AndreTheGiant]

if yes, does it have Differential backup capabilities?

I think the answer is no (but I've not used the last version of those script).

Maybe you can try to ask directly to the author ().

Andre

[lamw]

Unfortunately, there is no easy answer ... as mentioned, it'll depend on various factors: type of SAN (FC/iSCS), your workload on the VMs, etc,etc... This is something you would need to test, probably look at some of the statistics from the SAN's point of view to see how much traffic you might be driving, taking a look at the service times from the ESX(i) perspective during the hours you plan on executing the backups, are systems pretty idle ... or they busy on certain resources/etc....

It'll be different in every environment, one thing I can safely say is the latest version of ghettoVCB.sh and for that matter all the version are design to execute sequential backups of VMs from a list ... you can parallelize it if you so choose through your own means, but at any given moment, you'll be backing up 1 VM at a time and moving 1 VMDK at a time, so the amount of traffic should not be too significant unless you're saturating your SAN or using sharing iSCSI connection/etc.

I would suggest using the latest version of the script which is ghettoVCB.sh which contains a re-branching of code so you don't need a separate version for ESX(i) 3.5 and 4.0, take a look at the release notes for more information.

The script does not support any type of de-dupe / differential backups, this is not something that is capable with the tools that are available. You may want to look at other tools if you're interested in that such as VMware vDR or Veeam,etc.

=========================================================================

William Lam

VMware vExpert 2009

VMware ESX/ESXi scripts and resources at:

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