migrate from ext4 to zfs mirror (need some comment)

[b7842]

Hello, I am new to zfs. After reading some posts here, I got some knowledge about zfs.

My old build:
4TB red*2 (ext4) hosted at OMV on a esxi 5.5
these hard disks were passed thru to esxi directly

My new build: (Going to build in this week)
Brand new 4TB red*2 + g4400 + 32gb ecc ram + c236 MB
1) install FreeNas 9.10 to the usb drive and boot directly from the physical machine
2) start to build a Virtual Device with 2 brand new 4TB
3) Rsync the old data from the OMV to Freenas
4) Use the old 4TB*2 from OMV and build another Virtual device for mirror


Here are some questions:
1) For the log device, should i use USB thumb drive or SSD?
2) For the zfs performance, should I use the native c236 sata port or use hba 9211 8i?

Thank you

 

[snaptec]

1) do you really need a log? If yes, usb is no option.
2)sataport should be fine.
Except you have a case with a expansion backplane.


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[m0nkey_]

1) For the log device, should i use USB thumb drive or SSD?

Do you understand what you're saying? You probably mean SLOG device. Unless you're doing synchronous writes, it'll be pointless as it wouldn't be used.

 

[b7842]

1) do you really need a log? If yes, usb is no option.
2)sataport should be fine.
Except you have a case with a expansion backplane.
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After reading the below post, i knew that the SLOG can be saved at the zpool or outside the zpool.

Do you understand what you're saying? You probably mean SLOG device. Unless you're doing synchronous writes, it'll be pointless as it wouldn't be used.

https://forums.freenas.org/index.php?threads/some-insights-into-slog-zil-with-zfs-on-freenas.13633/
This post indicated that if the users move their SLOG to a ssd, they will achieve a better performance. Am i correct?

 

[snaptec]

That depends on your setup and configuration if a slog is a performance boost.

What do you want to do with the FN?


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[m0nkey_]

After reading the below post, i knew that the SLOG can be saved at the zpool or outside the zpool.
https://forums.freenas.org/index.php?threads/some-insights-into-slog-zil-with-zfs-on-freenas.13633/
This post indicated that if the users move their SLOG to a ssd, they will achieve a better performance. Am i correct?

Are you doing synchronous writes? It's a simple yes or no. If you don't understand what synchronous writes are, then you're just wasting an SSD.

 

[b7842]

That depends on your setup and configuration if a slog is a performance boost.

What do you want to do with the FN?


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Are you doing synchronous writes? It's a simple yes or no. If you don't understand what synchronous writes are, then you're just wasting an SSD.

If i need the NFS service (sync write is required in this service) , then i need to buy a SSD.
If i just use the SMB only, then i no need to buy a ssd.
Am i correct?

 

[snaptec]

Maybe, depends on your configuration and mount options.

You can use nfs with Sync writes without an ssd. And you can use nfs without sync writes.
Question is for what you will use it.

Just as file Sharing you may feel no differences, if you Have a ssd or Not.
As vm datastore for database workloads you will feel The slog.

But when you consider smb you will just do file sharing?


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[m0nkey_]

If i need the NFS service (sync write is required in this service) , then i need to buy a SSD.

False. You need it if you're doing sync writes. If you're doing basic file sharing, media, documents and whatnot. Adding a SSD will do jack shit. If however, you're running a NFS datastore for VMware ESXi, then yes, you need a SSD for a SLOG device. Typically you would get one that has some kind of powerloss protection.

 

[snaptec]

There is no NEED!
Slog is just an option.
It will work without with sync writes - but slower ;)
Just that new users don't misunderstand that.


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[SweetAndLow]

You can also just disable sync writes to the dataset and still use NFS. You just might have some issues if there is a sudden power loss.

Sent from my Nexus 5X using Tapatalk

 

[b7842]

You can also just disable sync writes to the dataset and still use NFS. You just might have some issues if there is a sudden power loss.

Sent from my Nexus 5X using Tapatalk

For the esxi NFS, it seems it force to use the sync option??

 

[SweetAndLow]

For the esxi NFS, it seems it force to use the sync option??

Yes this is true but if you set sync=disable for your dataset it just lies to the client that the data was synced. This will have better performance than a slog but in a power loss scenario you will lose any transaction groups that have not made their way to disk.

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