On Wednesday, 12 October 2016 4:03:27 PM AEDT Craig Sanders via luv-main wrote:
The failure modes of SSD are quite different to the failure modes of spinning media. I expect it will be some years before there is adequate research into how SSDs fail and some more years before filesystems develop to work around them. ZFS and WAFL do some interesting things to work around known failure modes of spinning media, they won't be as reliable on SSD as they might be because of the spinning media optimisation.
I'd still use some kind of raid-1/mirroring anyway, no matter what kind of drives I had. raid isn't a substitute for backups, but it does reduce the risk that you'll need to restore from backup (and the downtime and PITA-factor that goes along with restoring)
also, there's no way for ZFS to correct any detected errors if there's no redundancy.
The ZFS copies= feature is designed to operate in single-disk mode. The ZFS metadata has 1 more copy than the data, so even without using copies=2 you will have multiple copies of metadata on a single disk. But whether that does any good on SSD is anyone's guess at the moment.
i don't mind paying double for storage. it's a bit painful at purchase time, but that's quickly forgotten. and a lot less painful than the time and hassle required to restore from backup, and losing everything new or modified since the previous backup (nightly, but that's still up to a full day's worth of stuff that could be lost. Now that i've got rootfs on ZFS, I can snapshot frequently and backup more often with zfs send)
It's a pity that the options for RAID on laptops are so poor. Thinkpads used to have the option of buying a disk bay to replace the CD/DVD drive but I don't know if that is still available and it was always quite expensive. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/