ZFS as backup-storage for windows-systems - sync=disable vs optane, Flash

[Stril]

Hi!

I need a new storage as DR-backup for some windows-servers.
The goal is:

- Copy Diffs from NTFS-filer to ZFS-filer
- Take Snapshot
- Repeat

The system should have enough performance to have the possibility for a fast restore.

Can you give me some hints?

- ZIL
In the past, i have only been using systems with a fast SLOG-device, but here, sync=disable could be an option.
--> Is sync=disable always faster than sync=standard with optane-ZIL?
--> Is there any risk in my setup except loosing 10s of data?

- Full-Flash
--> Do you see any benefit of a full-flash-system with ZFS, or would you go with many spindles?

Thank you for your help!

Stril

 

[gea]

For the backup you can sync ntfs and ZFS via robocopy
or you can use iSCSI to use ZFS directly

For best performance use 10G
and enough RAM, 16GB and more

Zil
ZFS collects all small random writes in RAM to do large and fast sequential writes.
If you enable sync, you must do additional sync write logging to the Slog.
This is additional so always slower. Slog is not a cache but a writecache protector.
Writecache on ZFS is RAM and only RAM.

Without sync you loose up to last 4GB of writes (Open-ZFS) or 5s (Solaris).
ZFS is CopyOnWrite so no problem with a crash.

For a backup, spindles are perfect, SSDs are not needed.
If you want sync, add an Intel Optane as Slog (800P or better).
Such a config allows up to several 100 MByte/s (10G capable)
sync write performance.