jwinsor566
n00b
- Joined
- Feb 26, 2011
- Messages
- 13
Is there a lesser of two evils in this case... Sync =Disabled or Writeback Cache = on or does the use of either make your setup unsecure. I will be using this as a Backup Storage device for my backup software which does some file checking so if something was not there then it should find out and ask to have it sent again.As I understand the problem:
All (by the disk-subsystem) confirmed write operation should be really on disk.
ZFS is a Copy on Write system. That means that a data block is written to disk successfully
or the complete write is not done at all. This is needed to keep your data state always in a defined state.
If you have a power failure under such a condition, your currently written file is probably not lost (the
filesystem knows the former state and keep the former file version)
If ZFS asumes, the file is written to disk correctly and you have a power failure it could happen that
this file is damaged. Due to checksums ZFS may discover the problem but the file is damaged
If you disable sync at all, you have the additional problem, that all write operations of the last up to about 30s may be lost.
Secure way is to enable sync writes and disable write-back.
But with ZFS all data not affected by a current write is always save and even in case
of damaged files, ZFS knows about due to end to end checksums.
The last is the most important thing. Your data must be always ok or the OS must report an error-
thats why ZFS is unique.
Gea
I am thinking of keeping it set to Sync = Standard and enabling Writeback Cache because I have a SSD Log device and if I were to set the sync = Disabled it would stop using the SSD if I am reading the manuals correct.
Thanks for your input and fast replies.