Will Murnane wrote:
> On Mon, Sep 15, 2008 at 13:18, mike <[EMAIL PROTECTED]> wrote:
>
>> Everyone else: I get the stripe vs. raidz comparison now. Essentially
>> a stripe has no ditto blocks then?
>>
> "Ditto blocks" it has; this is ZFS' name for redundant metadata.
> There are multiple copies of directory entries and such, so that
> corrupting a single block can't cause you to lose the entire
> filesystem below that block, even on a single disk. But a stripe
> lacks parity blocks, which ZFS needs to recreate damaged data.
> Raidz{,2} have this, and mirrors have this, but single disks do not.
>
This is wrong... Ditto blocks are exactly what the name suggests,
duplicate data blocks. If you write 8KB and "copies=2" 16KB is written
to disk.
The primary purpose of ditto blocks is to provide data redundancy when
you do posses multiple disks, for instance on a laptop drive. If one
block becomes corrupt, ditto blocks can provide a duplicate block to
prevent data loss.
Ditto blocks are NOT just for metadata.
benr.
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