Will Murnane wrote: > On Tue, Sep 16, 2008 at 01:28, Ben Rockwood <[EMAIL PROTECTED]> wrote: > >> 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. >> > But by default copies=1, and only one block is written. > > >> 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 >> > "do not"? > >> block becomes corrupt, ditto blocks can provide a duplicate block to >> prevent data loss. >> > Yes, but my understanding is that this isn't a very good method of > providing redundancy; AIUI the two copies aren't guaranteed to be on > different disks, so if that disk dies you've lost all the copies of > that file. Not to mention the pool won't be importable with a missing > disk. > > >> Ditto blocks are NOT just for metadata. >> > True... but they aren't on (for all data) by default. You're right > that ditto blocks can be used to make multiple copies of data, but I > think they're a bad strategy for most situations. >
Ditto blocks are an excellent solution when you only have one disk. -- richard _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
