On Nov 19, 2013, at 11:35 PM, Martin <m_bt...@ml1.co.uk> wrote: > On 19/11/13 23:16, Duncan wrote: > >> So we have: >> >> 1) raid1 is exactly two copies of data, paired devices. >> >> 2) raid0 is a stripe exactly two devices wide (reinforced by to read a >> stripe takes only two devices), so again paired devices. > > Which is fine for some occasions and a very good start point. > > However, I'm sure there is a strong wish to be able to specify n-copies > of data/metadata spread across m devices. Or even to specify 'hot spares'.
Hot spares are worse than useless. Especially for raid10. The drive takes up space doing nothing but suck power, rather than adding space or performance. Somehow this idea comes from cheap companies who seem to think their data is so valuable they need hot spares, yet they don't have 24/7 staff on hand to do a hot swap. (As if the only problem that can occur is a dead drive.) So I think those companies can develop this otherwise unneeded feature. n-copies raid1 is a good idea and I think it's being worked on. Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
