NFS vs iSCSI for backups of ESXi VMs

[dairyengguy]

I am currently experimenting with FreeNAS as storage for holding snapshot-based backups of my ESXi hosted VMs. I have been reading about NFS vs iSCSI and had some questions about them.

This is the thread I have been reading: https://forums.freenas.org/index.ph...xi-nfs-so-slow-and-why-is-iscsi-faster.12506/

Basically I understand that NFS with sync writes enabled is a safer option when running your VMs from the datastore, and is almost absolutely necessary for keeping the data safe on a running VM. How will this affect my situation in which I am essentially just copying snapshots from another datastore to FreeNAS? Is this only going to be an issue in the event of a power outage? Or do I need to invest in a good SLOG and use NFS with sync writes enabled?

Thanks in advance!

edit: for clarity.

 

[sfcredfox]

This is what comes to my mind:

I'm thinking about what the snapshot actually is. While it's only a backup, it's something you expect to be accurate if you were to restore from it. If you end up with a compromised live dataset and an inconsistent backup data set, you're still screwed.

IMO, I would recommend following the advice of setting the SYNC to always so you know that the snapshot data is fully written and in a consistent state for what your host/originator thinks is there.

And yes, you'll want a good SLOG device. Everyone recommends a capacitor backup enterprise SSD for the SLOG since most SSDs cache things before writing to the slower flash.

 

[dairyengguy]

I definitely agree with you. However, if I am only risking data corrupted backups on a power outage, I can live with that. If there is a power outage during a backup, I will be ditching that backup set anyway and immediately creating a new one once power is restored. That is assuming that I am not recovering an older, known good backup.

However, if there is further risk (perhaps I don't fully understand the difference here), then I will definitely go with NFS and a SLOG for performance.

As an aside, are there any enterprise SSDs that are affordable and recommended here? Or even better is there a link to a thread recommending some?

 

[dairyengguy]

As an aside, are there any enterprise SSDs that are affordable and recommended here? Or even better is there a link to a thread recommending some?

Nm. Did some more searching and notice that the Intel S3700 is recommended frequently. Is that still a good choice? Looks relatively cheap for some peace of mind.

 

[Mlovelace]

If you are copying snapshots for backup purposes why the concern for performance? I would force sync, copy the snapshots and see if the times are acceptable. If not then add the SLOG device.

 

[dairyengguy]

If you are copying snapshots for backup purposes why the concern for performance? I would force sync, copy the snapshots and see if the times are acceptable. If not then add the SLOG device.

I am running iSCSI as a test right now, and my backups all run in about 3 hours barring any complications. I am going on the assumption (from previous tests) that NFS with sync enabled will be about half the speed. While 6 hours isn't terrible, I much prefer the 3, especially considering room for expansion.

TL;DR Basically already did what you suggested and decided that if I go sync, I need a SLOG

 

[dairyengguy]

Also, if I have read everything correctly, it may be really cheap (<$200)

http://www.newegg.com/Product/Product.aspx?Item=N82E16820167139