# Raid



## kaymann (Sep 23, 2012)

erro, as a total side note not related to moving a catalog:

I would have made a RAID of the two SSDs. If you think your single SSDs are fast now you would not believe the speed of a RAID0 SSD Array.  The beauty of an RAID0 is your speed nearly doubles as well as the capacity of the resulting drive.  you definitely would want to use a SATA6 board and cables to max your throughput.  The speed of resulting systems we build is unbelievable compared to even a comparable single SSD drive system.

After creating a RAID0 array a catalog move would be unnecessary (a ghost would be necessary though - we do it for our customers all the time).

And your move guide is very complete covering all the pitfalls and necessary cautions - excellent job!

_*Mod note - thread created from this thread: http://www.lightroomqueen.com/community/showthread.php?17199-Guide-How-to-move-Lightroom-s-catalog*_


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## erro (Sep 23, 2012)

I think the speed is fast enough as it is. But I get your point. Two disks in RAID0 will, I think (?), on the other hand double the probability of failure of that "one" disk, won't it? And since my purpose of buying a second SSD was to overcome the fact that my first SSD was running out of space, RAID0 wouldn't really solve that problem.


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## kaymann (Sep 23, 2012)

RAID0 is additive in other words (120G + 120G) array = 240G RAID0.  The zero in RAID stands for zero additional redundancy.

RAID0 does not increase the chance of failure but if one disk fails the RAID is broken and that means a rebuild of the array. So the risk is exactly same.  Right now if your C drive fails you will have to reinstall.  If your "Lr" drive fails you will have to pull out a backup of your catalog.  However, that is why we back up our catalogs anyway.

Lets remember with SSD their are no spinning parts or moving heads so when they are on they are on...  Whether in an array or not they will be on and accessed.  The difference in a HDD and a SSD array is a HDD RAID could arguably cause more head wear and tear. Spin time would be the exactly the same, but head movement could oncrease.  In SSD array you have removed the head movement so wear and tear is left to the amount of on time.

An analogy could be the argument over a married couples use of toothpaste. I like "Crest", spouse likes "Aquafresh".  I like the cap on spouse leaves it off.  Let's just buy two tubes of toothpaste - no we can't we will spend twice as much on toothpaste - no we won't each tube will empty half as fast, for the same amount of tubes purchased over the same amount of time.

With SSDs the access "time" will be split between the two drives.  Remember your going to finish faster therefore access time is reduced for each drive but overall both drives add up to the same amount of time).

"Disk" space in a RAID0 is the smallest of the drives multiplied by the number of drives (almost - a little for overhead).
"Disk" speed in a RAID0 is speed of the slowest drive multiplied by the number of drives (almost - a little for overhead).
"SSD" MTF (Mean Time to Failure) is a factor of On Time and On/Off state changes, Temperature and Access Counts. A RAID0 has little effect on "changing" any of these factors.


Robert, I hope this makes sense.  I frequently have this conversation with our customers and again great tutorial on catalog movement.


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## erro (Sep 23, 2012)

OK, I mixed up RAID 0 and 1.

But still, my point is that now I have two separate disks. If one of those disks fail it will only affect that disk. If I RAID the two disks, be it RAID 0 or 1, a failure will effect that entire "disk" concisting of two disks.

But it is off-topic now, since my plan (or article) was never to use RAID at all. Thanks for the comments though.


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## DaveS (Sep 23, 2012)

What you are really looking for if you are going to do raid, would be Raid1 or Mirroring.   If either half breaks, you replace the failed drive and then the array will re-sync to the replaced drive.     Windows 7 can do this natively in the O/S.  You set it up in the computer management program.  BTW, we're only up to SATA 3, which is 6 gbits/second.  But, for sure, if you are using a newer ssd, sata 3 is the ticket here.   

Now, one thing to consider with raid and ssd's.  Depending on how you set the mirror up (hardware, software etc) the Trim command may not be available anymore for your ssd's in the raid.   This is something you want to avoid, as it will limit the life of the ssd's.    Trim is a command (Windows 7 for example supports it) that tells the SSD what portions of the drive are available for garbage collection and recycling.    SSD's don't delete single files in the way that a regular disk does, but have to erase in big chunks.  Trim tells the SSD what portions of the drive are availeble for this.


In my system, i have an SSD for my C drive (apps and operating system).  Lightroom is installed on the SSD and my catalog is  also on that drive (making updates to the internal database fairly fast).   My photos (and my weekly (or more often if i do a lot of work) lightroom catalog backups) are on the mirrored D drive ( a pair of 500GB drives).      Daily my d drive is synced (using a windows derivative of the unix RSYNC command) to a mirrored drive on my Linux file server (yes, there is a bit of the anal database admin here), which is in turn backed up weekly to an external drives.   There are two of these, one i keep at home, the other lives at my in-law's house and are swapped every couple of months or so.

Dave.


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## kaymann (Sep 24, 2012)

Dave yes you are right I fogot the G in 6G and I do have a RAID0 for my sys (boot to desktop don't blink you'll miss it) and a mirror for the data (build them all the time figured I could at least have one for myself) and a copy of the data in a fireproof safe.  Keeping one at my out-laws house never thought of that.  Actually that is a great idea as they live frairly close so that would work as well - he has a fireproof safe also. 

We should let this go as I should have started another thread - this is more than looking like a hijack.  Erro, I will repeat your tutorial was great.


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