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gshaw
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Direct SAN not as fast as NBD mode?

Post by gshaw »

Just changed our Veeam server to direct SAN mode from NBD mode, all working fine but the jobs are a touch slower? Overall processing rate down to 486MB\s from 537MB\s, job for 7 VMs takes around 5-6 minutes longer.

Using one 1Gb iSCSI connection with two network cards (one per iSCSI subnet as our SAN has active-active controllers) writing to a 5 disk RAID5 set using 2TB SATA disks. Can take those out the equation as the speed was faster with the same disks before so must be using the direct SAN connection somehow.

Granted the jobs aren't slow by any means but just wondering why going direct SAN would slow things down as opposed to NBD mode which is meant to be a lot slower?

Vitaliy S.
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Re: Direct SAN not as fast as NBD mode?

Post by Vitaliy S. »

Hi Gerrard,

Direct SAN mode should always be faster compared to NBD mode, please see our existing topic talking about possible tweaks that should improve SAN based backup jobs performance: Veeam Backup & Fast SCP with a Dell MD3000i (nevermind the title)

Also I would recommend comparing full runs in both modes (of course if it is possible), as incremental mode performance may vary from time time depending on the amount of changes made to the VMs being backed up etc.

Thanks.

tsightler
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Re: Direct SAN not as fast as NBD mode?

Post by tsightler »

I'm assuming all of the quoted speeds are for "incrementals". It's extremely difficult to compare because the amount of data process is significantly less than the reported transfer rate (which is just size-of-backed-up-data/time). SAN mode does seem to have slightly more "setup" overhead because of the way vStorage API has to map out the VMDK. This isn't required for NBD mode.

Also, is the target storage also iSCSI in both the SAN and Network mode testing?

gshaw
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Re: Direct SAN not as fast as NBD mode?

Post by gshaw »

Backup target storage is local disk in both cases.

Could well be the setup process that's taking the extra time, that said as we add more VMs the SAN mode should be a lot more efficient on the heavier VMDKs (Exchange, file server etc) than NBD so it might balance out?

Vitaliy S.
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Re: Direct SAN not as fast as NBD mode?

Post by Vitaliy S. »

gshaw wrote:Could well be the setup process that's taking the extra time
You may want to compare log files for both job and see what is taking extra time (our support team can assist you with this), however I do agree with Tom that incremental job passes are hard to compare.

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