bad idea? (nMP backup storage related)

Discussion in 'Mac Pro' started by analog guy, Feb 7, 2014.

  1. analog guy macrumors 6502

    Mar 6, 2009
    got a question related to backing up my nMP. i'm re-thinking my back-up strategy with this change.

    primary data drives for active/recent projects are 2x1TB 840 EVOs in RAID0. i connect them via my sonnet echo express iii-d; they reside on a tempo pro SSD card.

    i've got a tempo SSD card (slightly slower rated speed vs the tempo pro). i was thinking of putting the SSD from my older mac pro on that.

    i back up to time capsule, so there's that.

    i have a 2TB 2.5" WD green drive. i was thinking i could put it on the tempo SSD card (along with that other SSD from my old Mac Pro) and back up the RAID0 to it.

    pros: clean setup.
    cons: one enclosure (though i still have my TC files as a 2nd backup). 2.5" HDD tops out at 2TB and is higher $/GB than a 3.5" drive, though i'd need a 3.5" enclosure if i go the 3.5" route.

    have i missed anything?

    i welcome any thoughts/suggestions.

    (the Tempo Pro SSD and Tempo SSD have SSD in their name but I see no reason why any 2.5" drive won't work...unless it is a power issue.)
  2. VirtualRain macrumors 603


    Aug 1, 2008
    Vancouver, BC
    Sounds like a great setup to me. The only potential issue with it, may be if there's some kind of power surge or spectacular failure of the PSU in the enclosure that cooks both the SSDs and the HD at the same time... but that's probably a risk worth taking for the elegance of the solution (and you mention Time Machine so maybe there's another backup anyway?).

    At any rate, I would go for it. :)
  3. deconstruct60 macrumors 604

    Mar 10, 2009
    if doing a version backup then 2TB isn't really enough to back up a 2x 1TB stripe. The amount of data in the backup over time is going to exceed the primary source drive's capacity ( whether it is a 'logical' drive or a physical one. ). Backing up 2TB to 3TB means can keep deltas and changes over time (e.g., suitable Time Machine target). Backing up 2TB to 2TB mean doing more so "cloning" than general backups.

    Having only a clone is OK as long as willing to deal with the limitations. ( it is better than no backup at all. )

    The manual for The tempo says it can deal with HDDs. If the drive has lots of hours on it then changing the default orienation may be something to look out for.
  4. analog guy thread starter macrumors 6502

    Mar 6, 2009
    thanks for the comments.

    sorry if my original post was unclear. i have a separate time machine backup (time capsule). i was thinking this 2TB drive would be a (daily) clone of the 2TB RAID0.

    if the RAID0 fails, then the 2TB drive could step right in. the TM backup should be happening hourly and should do version control.

    using the WD green 2.5" drive for the TM backup might be a bit faster than using the TC, but then while i could make an image on the TC it would not be a clone and would involve another step in the event of an issue.

    an issue i see: off-site backups (e.g. swapping the clone periodically) are a bit more difficult -- have to open up the sonnet case. could always use an off-site/on-line service, i guess.

    thanks for the thoughts!
  5. deconstruct60, Feb 8, 2014
    Last edited: Feb 8, 2014

    deconstruct60 macrumors 604

    Mar 10, 2009
    But you mentioned that the TM would be the "2nd backup". It is OK (allows quick recovery in reduced capacity/bandwidth mode) but this really isn't a second one. There is lots of data on the TM repository that only has one copy so this really isn't a second one. It is a subset and that archive data is toast if the Time Capsule's drive craps out. (and it will eventually ).

    You can take measures to periodically clone your TM drive but that would be another external drive. A real back-up is going to involved another external drive that is larger than 2TB. This clone is more so a temporary "fail over" drive so can keep working on more recent stuff. An asymmetric (and perhaps slightly out of sync) RAID 1-like mirroring. A "cheaper" , but faster in non-fail mode, RAID 10 (or technically 01 ).

    If wanted to failover fast and keep the speed could just do RAID 10 with four SSDs. This is more cost effective if OK with the gaps that the clone sequencing can leave.
  6. analog guy thread starter macrumors 6502

    Mar 6, 2009
    I guess I don't follow you. Sure the time capsule drive could fail, as could a member of the RAID0 set and the 2tb clone drive, but the main night I am worried about is losing all of them at once.

    The clone drive allows me to continue working, having lost at most a few hours of work --and those incremental files should be in the TM backup.

    If the clone drive fails I get another one (not too much urgency as I have the slower TC backup. If the TC drive fails I get another one (a bit more urgency as it is the only one with the hourly versions).

    I don't want to buy 2 more SSDs for a 4-drive RAID10 (though I do like and have used raid10 extensively).

    I am not aware of any >2tb 2.5 drives that I could use for something more than a clone of my RAID0 setup.

    If I have misunderstood anything, I am sorry.

    Instant failover is nice but I am not running life support systems so I can, and have, dealt with a short amount of downtime.

    Thank you!
  7. deconstruct60, Feb 8, 2014
    Last edited: Feb 8, 2014

    deconstruct60 macrumors 604

    Mar 10, 2009
    Being in a state of 'back up' should result in there being more than one copy of something. If there is only one copy then any single failure can wipe out the data. So if later find yourself in a state of being wiped out.... you were not backed up.

    Your 'clone' is really a variation of RAID 1. RAID 1 isn't a back-up (nor variations or parity RAID). It is a faster failover than restore from scratch, but it really isn't a back-up. It can serve as s a "better than nothing" back-up in that there is a duplicate of a subset, but there is still another subset of non-duplicated data.

    That is called 'failover' not backup. What you primarily have is a faster failover service that provides high availability; not a back-up. That is what RAID-1 (and derivatives ) primarily provides.

    You have one failover service ( this 2TB HDD clone) and one back-up service (the Time capsule drive).

    All the drives are going to fail eventually. Single points of failure wiping out what was perceived as redundant (but actually not) is what core issue is.

    I'm not saying you "have to" buy SSDs. I"m saying that is what you are approximating in this set up. You are building a variation on RAID 10 that has some trade-offs to get to a cheaper price point. Those may work at an acceptable level of risk for you. They may not for others. But in order to do a proper risk assessment you need to label what you have for what it actually is; not what it isn't.

    Therein lies the rub.... If need another archival backup then at this point need 3.5" drives and Tempo isn't necessarily going to help. ( > 2TB 2.5" are coming; just aren't here yet). I think there are some TB expansion boxes that have drive sleds built in. But that is a different track than what you have already sunk money into.

    Time Machine + a single Time Capsule drive is more so a "better than nothing" solution than a robust back-up service. They are useful in that most folks do nothing which is worse. Over an extended period of time folks tend to get lulled into a notion that they are covered up until they find out they really covered any better than when the data was on the primary drive in their Mac in just one place.
  8. analog guy thread starter macrumors 6502

    Mar 6, 2009
    thanks for your post.

    i guess....but basically i have a full backup (clone) which is at most 8-12h old (a risk, sure, but OK in my environment) AND i have TC, which is a versioned backup. that's 2.

    i don't really see why you keep referring to one.

    i understand...sort of. it's not really the same as RAID10 as if i had some data corruption that occurs today it would plague all drives in RAID10, but in the RAID0 + nightly clone the nightly clone would NOT get today's corruption (if detected today).'s different.
    RAID10 is immediate failover protection, and it works.

    i guess this is where we disagree. you're saying my proposed solution is effectively RAID10, but i think it is a bit different -- and that bit is significant (for me).

    agreed, but it's a clone, not RAID1. the real-time element of RAID1 is a distinction. there is lots of value in RAID1, but my solution is not real-time and that can be perceived as a feature.

    true, but i am still seeing TWO points of failure. the TC would have to fail AND the clone would have to fail, in addition to one or both of the RAID0 drives failing, at the same time.

    i know you didn't say i have to buy 2 SSDs, but you mentioned RAID10 and the only way to do that (without bringing all drives down to the performance of the worst drive) is to add 2 more SSDs. that's a non-starter for me. just not necessary.

    agreed that it is about acceptable risk.

    i've tested several of those expansion boxes. they offer poor performance with 2 SSDs in RAID0, unfortunately. so...they're non-starters.

    anyone who does not test their back-ups has other issues. TC has helped me restore prior versions and do a complete restore.

    sure, people have problems, but one could have problems in any automated solution that they do not test. i would not dismiss TC out of hand. i think it still counts as one (of 2) backups in the above scenario.

    not trying to be contentious at all--i appreciate the discussion. i am grateful for your comments and wanted to articulate my opinions as counter-points. if i am wrong in any of the above i am open to learning.

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