zfs checksum question (fletcher2 vs fletcher4 vs sha256)

[jazzsm...@gmail.com]

As I understand it, the Solaris default zfs checksum changed from fletcher2 to fletcher4.  

However, the MacZFS checksum default = on is fletcher2 per the man page.  Is anyone using fletcher4 or sha256 as their default checksum?  

More concerned about data integrity than performance.  Most of my transactions are read only anyways.

Also, you guys are doing a great job!  I've been using MacZFS for over a year with no issues.

OS X 10.7.5 Server

Dell T3500

Xeon w3550 (quad core)

24 GB RAM

(1) Intel SSD 160GB (boot)

(4) Seagate 3 TB (zfs mirror)

Fred

[Richard Elling]

On Jun 2, 2013, at 6:50 PM, jazzsm...@gmail.com wrote:

As I understand it, the Solaris default zfs checksum changed from fletcher2 to fletcher4.  

This change was driven by paranoia rather than observed behaviour. What we observe is that corruptions for modern disk storage systems occur as massive corruptions, easily detected by even simple checks. For example, modern HDDs can detect and correct on the order of 32 bytes per sector. So it is better to worry about spending your lottery winnings rather than worrying about coverage single, random bit flip that exactly hits the weakness of fletcher2. For those who enjoy worrying, sha-256 should reduce, but not eliminate the concern.

  -- richard

However, the MacZFS checksum default = on is fletcher2 per the man page.  Is anyone using fletcher4 or sha256 as their default checksum?  

More concerned about data integrity than performance.  Most of my transactions are read only anyways.

Also, you guys are doing a great job!  I've been using MacZFS for over a year with no issues.

OS X 10.7.5 Server

Dell T3500

Xeon w3550 (quad core)

24 GB RAM

(1) Intel SSD 160GB (boot)

(4) Seagate 3 TB (zfs mirror)

Fred

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