2008/3/7, Paul Kraus <[EMAIL PROTECTED]>: > On Thu, Mar 6, 2008 at 8:56 PM, MC <[EMAIL PROTECTED]> wrote: > > > 1. In zfs can you currently add more disks to an existing raidz? This is > important to me > > as i slowly add disks to my system one at a time. > > > > No, but solaris and linux raid5 can do this (in linux, grow with mdadm). > > > Be aware that growing an SLVM / DiskSuite RAID5 doesn't really > grow the RAID5 set, it just concats more components onto the end of > it. If those components are mirrors then you still have redundancy, if > they aren't then you don't for that data that ends up out there. I > don't consider growing RIAD5 this was with DiskSuite a good way to go, > short or long term. >
No, that is not how it works. If you grow a RAID5 set the new data is concatenated to the original RAID5, but it IS protected by the parity in the RAID5 set. You have redundancy but not the best performance. >From the docs: http://docs.sun.com/app/docs/doc/816-4520/about-raid5-1?a=view You can expand a RAID-5 volume by concatenating additional components to the volume. Concatenating a new component to an existing RAID-5 volume decreases the overall performance of the volume because the data on concatenations is sequential. Data is not striped across all components. The original components of the volume have data and parity striped across all components. This striping is lost for the concatenated component. However, the data is still recoverable from errors because the parity is used during the component I/O. The resulting RAID-5 volume continues to handle a single component failure. Concatenated components also differ in the sense that they do not have parity striped on any of the regions. Thus, the entire contents of the component are available for data. Any performance enhancements for large or sequential writes are lost when components are concatenated. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
