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SoftRAID Volumes
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After having the internal hard drive fail in my iMac (successfully predicted by SoftRAID - thank you!) I then discovered some weaknesses in my backup strategy. It turned out that the Drobo 5D connected by Thunderbolt which had my Time Machine backup on it could not be seen by the "restore from Time Machine" application when booted from the
Recovery Partion. It also could not be seen when I plugged the 5D in with a USB 3 cable. It did work with a USB 2 cable, but this was very slow to restore.
As I try to get things back up and running (collect the iMac today from the Apple Store) I'm looking to change a few things. The data on my Thunderbay 4 uses raid 1+0 but I don't have a spare set of drives. I'm thinking this might be a better solution than Time Machine in terms of speed of getting back up and running.
I use Carbon Copy Cloner for my boot drive, though I had a few issues with my clone after I discovered the problem with the internal drive, possibly because the "safety net " had overfilled the drive, and the system was running very slowly, made worse by the fact it was a 5400 rpm drive and both Dropbox and iCloud Drive were trying to sync. Eventually it sorted itself out, at least to be usable.
In the light of these issues / experiences, I wonder what the best strategy is going forward. Would replacing the Drobo 5D with a Thunderbay 4 using RAID 5 be any better with Time Machine restoring in recovery mode? Would it recognise a SoftRAID volume? Or should I simply consider Time Machine only for recovering individual files accidentally deleted etc - and use either Carbon Copy Cloner or a spare set of SoftRAID drives for my main disaster recovery? Which would be better - CCC or a spare set of Raid 1+0 drives? I read that CCC can check the destination for corruption, and can be scheduled whereas a spare raid set would require me to remember to swap the drives over (and my only criticism of the Thunderbay 4 is that the drives have to be screwed into trays, the tool-less method of inserting drives into the Drobo 5D is much better).
I'd really appreciate some advice on this. Thank you.
Posted : 24/12/2015 1:31 am
Backup strategies are unique to each situation. Its always a balance between protecting against failures, against corruption and the speed to restore data to a working state.
RAID 1+0 is always a good RAID when you are most concerned about data integrity, reliability and recoverability. RAID 5 is faster, but harder to perform a data recovery from if there is a serious problem, or it multiple disks fail.
Time Machine works well on SoftRAID volumes, both RAID and non RAID. There is one limitation in that Time Machine encryption does not work on SoftRAID volumes.
One factor users often forget when forming a backup strategy is corruption or damaged/deleted files. Both Time Machine and correct archive strategies are valid strategies to protect against this kind of problem.
Time Machine is not particularly fast, but can be good when you have a large enough Time Machine volume for recovering deleted/damaged files. RAID 5 works well for this.
Carbon Copy Cloner (or SuperDuper) are good for backing up copies of bootable volumes. Chronosync is also a good alternative.
Another option is to have the most critical data copied, or synch'd to a standalone hard drive, which is kept off site. Your comment about enclosures that use sleds is a valid one. Keep in mind that the sleds help protect against static damage, improper insertion, etc. So they have their purpose. Most manufactures do offer extra trays for a reasonable price, and OWC certainly has spare trays available.
One recommendation to consider is replacing your internal HDD with an SSD, if you could. It makes a huge difference in the performance of an iMac.
Sorry we can't give actual specifics on this kind of subject, as every scenario really is different, but hopefully the generic advice above helps you select the optimal scenario for your requirements. ;-)
Posted : 24/12/2015 1:55 am
Topic starter
Thank you for the reply. Could you confirm whether or not Time Machine can be restored (either when booting from Recovery Partition, or when running Migration Assistant) from a SoftRAID volume.
The reason I ask is that I've had issues with the Drobo not appearing when connected via USB 3 or Thunderbolt, but also my SoftRAID volume which is made up of drives in the Thunderbay 4 in a RAID 1+0 has OS X Server Time Machine backups on it which don't appear either.
Nobody, including Apple, seem to specify what will and won't work in this situation.
The problem is, that no single drive is big enough for Time Machine, yet it seems TIme Machine doesn't show these volumes under various circumstances when booted in recovery or when running Migration Assistant. Having run into this problem, I want to make sure that whatever option I choose from now on, will allow it to work in this situation, and if possible using a fast connection (unlike the Drobo 5D which will only work with USB 2).
Posted : 24/12/2015 5:33 pm
SoftRAID volumes do not have recovery partitions.
We can test for this specific use case for you next year, but we have not had any complaints about Time Machine not being able to restore to or from a SoftRAID volume.
Posted : 24/12/2015 6:52 pm
