RAID-0 Question (Mac)

Need RAID-0 expert with Apple experience.

Think I am exceeding my inherent CPU  or  bus speeds.

Therefore, do not think the magic bullet of beefing up my RAID-0 will help.
(hope I am wrong about that)

Macbook Pro one year old:
OS 10.10.3  (Yosemite)
CPU  2.6 GHz  Intel Core i7
Memory 16 GB 1600 MHz DDR3
L2 Cache 256 KB
L3 Cache 6 MB
Memory 1 TB SSD

Am using Carbon Copy Cloner utility for a 100% clone backup.

Works great, takes 3-minutes to backup my main internal SSD  (10 GB )

My input to CCC is a RAID-0 of two USB3 spinning drives.

My output of CCC goes to a RAID-0 of two Thunderbolt-connected SSDs.

My friend has a similar Mac with 365-GB of stuff to backup using CCC.

Takes him 73 minutes to backup - - - intolerable.

Just for kicks, trying to help him shorten that backup time.


If I beef up both RAIDs to four drives instead of the present two drives, is that likely to shorten his backup time to 40-minutes?

Possibly I have hit a stone wall with the computer itself, so improving the RAIDs might not help?
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Backup speed is most affected by the number and sizes of files.   Your friend probably simply has lots of smaller files, so it is going to take longer.    As you have the same hardware, O/S, and RAID configuration, it is the nature of the data you are backing up.

 Do a test to prove it. Each of you copy the data you want to backup to /dev/null   This puts it in the bit bucket and eliminates the target backup devices from the equation.    How long does it take to just read the data each of you want to back up.  I'm betting it will take significantly longer on   your friend's system.   If it does, then this proves it is not a backup problem he/she has, but it is just the nature of the data itself.

If you want more speed, then use RAID1.  RAID1 will be TWICE as fast on reads than RAID0.  In fact, it  might be more than twice as fast on your friends system. [OSX has read load balancing] As for writes, it will be slower than RAID0, but in grand scheme of things it will be faster overall to have RAID1 instead of RAID0.   Yes, you lose capacity, but you are also protected against data loss if (no WHEN) you have an unreadable block on a disks, or lose a drive.  With your RAID0 config, lose a drive, you have 100% data loss.

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Davis McCarnOwnerCommented:
I am going to disagree with dlethe and point out several things:

The fastest laptop hard disk drive I have ever benchmarked delivered 149MBps and it was a Seagate hybrid HDD.  For traditional drives, I have seen 125MBps; but, a more realistic number for a production unit (meaning what Apple put in the MacBook) is about 105MBps.
For desktop drives, I have seen 190MBps and Passmark claims that some SSD's have reached 14,000+MBps ( )
USB3 is capable of 640MBps and Thunderbolt in dual channel mode will peak at 2,500MBps.

Why all of this matters is that a calculation of reading 365GB at 105MBps results in 57.9 minutes which does not include any overhead for the backup process or the speed of the destination drive(s) and becomes an immutable wall unless we do something about the device(s) speeds.  Another factor, ironically, is that once we reach the limits of the USB or Thunderbolt interfaces, money spent on faster drives is wasted.

So, first and foremost, if you want to speed up his CCC job, replace the internal HDD with an SSD which will remove the raw speed bottleneck inside the MacBook.

After that, if improvements are still needed in the external devices, we have to have the exact make and model numbers of both the units and the drives installed inside them.

P.S.  SuperSenile, there is virtually no way your stuff fits on a 10GB SSD!  You ought to look closely at your Mac as I suspect you are not backing up the second hard disk drive.
Davis - I based this on the authors post that this was only one year, so it is the 2014  retina MBP with the 1TB PCIe x 4 bus SSD. This  "SSD" will sustain over 1000MByte/sec throughput on published independent benchmarks.  It is not a SATA-attached SSD.

As for the output device, thunderbolt won't be the constraint since it is over 500MB/sec.   The USB-attached disks will be the bottleneck.  CCC creates a filesystem, so the output is going to be doing a lot of small block I/Os, and seeks, and this certainly won't be taking advantage of multiple threads and any significant queueing of I/O.

    But good catch on the authors 3-minute backup.  No  WAY is the author backing up his entire O/S.    In any event, I don't see any problem other than the author has miscalculated how much time his system takes to backup because the author is not backing up as much data as his friend.

(Here is another way to do a faster backup,  backup to a tar file on the local system, and then copy the tarball to the external disk.  You will get full throughput because there will be no random I/Os and it will be large block I/O writes).

Also to clarify my test, you time the read from the data already backed up from the external drives, not the internal SSD.  This will verify how long it takes to deal with the random I/O and chunk sizes of the filesystem.
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SuperSenileAuthor Commented:
Thanks again diethe - - - I did not think this was a "solvable" problem, but we are getting closer every day to being able to solve problems like this.
Davis McCarnOwnerCommented:
Just because he has a recent MBP doesn't necessarily mean he (or his friend) have SSD's; but, here is a freebie that ought to get us some real numbers:
Hopefully, it can also test the external units, too; though we both need their specifics as well.
SuperSenileAuthor Commented:
I don't have the foggiest idea what  "Please enter a body for this comment" means, I guess it is just more obfuscation by the people who run EE.

They never heard of the "KISS principle".   ;-)
Thomas RushCommented:
Be aware that going from a 2-drive RAID 0 to a 4-drive RAID 0, you will be at least doubling the chance of a catastrophic failure: that is, doubling (or more) your chance of losing *all* your data.  I wouldn't want this on my production machine, and if I had it there, I sure wouldn't want it on my backup data too.
SuperSenileAuthor Commented:
Hi SelfGovern - you bring up an interesting point which I will address shortly.

Yesterday I closed out this thread and awarded the partial "solution" to "dlethe" because I believe the problem to be basically unsolvable considering todays hardware and software.

Both me and my friend run SSD, his Mac is slightly older than mine, he has 500-GB of internal SSD while I have 1000-GB of internal SSD.

We both run "Carbon Copy Cloner" in   _clone_   mode to backup all hidden files, hard-links, EFI partitions, etc.

We both have the problem of unequal file sizes, everything from myriad tiny files to big monster files, a real backup nightmare.

Your Interesting Point
I do not worry too much about sudden failure of the RAID-0  SSDs because:

1) in my knee-jerk opinion, the failure would be obvious, so I would just replace the bad SSD drive and create another backup. Might happen once every six months.

2) tendency of todays modern SSDs is to fail evenly and gradually when contrasted to a mechanical spinning drive - - - we both keep our eyes on the steady deterioration of our SSDs with the $50  "Consultant" version of "DriveDx".

For example, my 6-year old 17-inch MacBook Pro supposedly has 95% of its SSD life still "left" according to the  S.M.A.R.T. program analysis of that old 500-GB internal SSD by the utility "DriveDx".

Steady "up time" of that SSD is 8-months, according to DriveDx.

I think the main villain causing  l-o-n-g  backups is just the relatively slow clock speeds of todays CPUs - - - "your milage may differ".   ;-)
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