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Hard drive, raid, cache - confused

allan53

allan53

macrumors regular
Original poster
Jul 22, 2002
167
13
New Hampshire
When my new 6 core Mac Pro (16 gb of ram) arrives next week, I will take the ssd and 2 hard drives from my old Mac Pro and put them into the new one.

I will have my system, apps, and documents on the ssd. I will have plenty of room to move backups and lesser used items to the 1 tb drive that comes with the Mac Pro.

That leaves me with 2 500 gb internal drives and a question about cache for Photoshop and Nikon NX2. I know cache should be on a fast drive so I could get a small ssd drive to use for that. Or I could make the 2 500 gb drives into a striped raid and use that.

Obviously it would be cheaper not to buy another ssd drive. I am trying to speed up my work, and buying the new Mac Pro will make the biggest difference. Can someone tell me if I would notice a slowdown using the raid?

If the ssd is some much faster, would it be o.k. to put the caches on the ssd drive I already have? I have always read that it is best to put cache on a drive that does not contain the documents you are working on as the read/write of cache will slow me down.

Kind of confused - never used a raid before and I know having the cache on an ssd would be quicker than having it on a hard drive.

Allan
www.nebirds.com
 
I wrote quite a bit of thoughts on scratch in other threads so might want to check out this one on HDD thoughts and scratch
https://forums.macrumors.com/threads/1002465/


now cache is something that LightRoom and Bridge use quite a bit of

scratch is something that PS uses

the quick cache is something written to disc then used to read from as needed as example lightroom cache could be read over and over for a long time as long as those images remain their ?
and scratch is more temporary space needed so its written and read to a lot and is very very short term like the current file you are working on

I have no idea if NX2 has cache or scratch setup ? I have played with it but thats it chances are though like LR or C1 the temp files if they are cache or scratch files will be quicker on a modern quick SSD and mainly cause of the access time more than the throughput


read my above link first then can try to answer more if you need :)


in quick not sure that PS scratch on a SSD is good or not ? I think its quicker but at how much cost and how much vs a raid 0 scratch ?

their is some question will it beat the heck and short life a SSD ? part of me thinks it wont and even if it does a bit the speed gain is worth it ?
the question is what is the speed of your old SSD ? as write and read speeds are important for cache IMHO :)

also is this a work setup you make money off ? or do shaving a few seconds matter in PS matter ?
 
VirtualRain said:
I assume by "cache" you mean "scratch"?

The faster your scratch volume, the better. So if you have enough spare capacity on your SSD for scratch (10-20GB?), go for it. Otherwise, your idea of using the pair of 500GB drives in a RAID0 array for a scratch volume is good also.

Here's some benchmarking done on MPG...
http://macperformanceguide.com/OptimizingPhotoshop-SSD.html
Click to expand...

Cache stays on the hard drive till it is cleared off. I think it is different than scratch as I think scratch gets deleted automatically.

I would want 60-80 gb for cache.

Thanks for the link. I still find it confusing as he talks about dual ssds. I know this would be better than a 2 drive raid, but I wonder if it would be faster if I only have 1 ssd.
 
Honumaui said:
now cache is something that LightRoom and Bridge use quite a bit of

scratch is something that PS uses

the quick cache is something written to disc then used to read from as needed as example lightroom cache could be read over and over for a long time as long as those images remain their ?
and scratch is more temporary space needed so its written and read to a lot and is very very short term like the current file you are working on

I have no idea if NX2 has cache or scratch setup ? I have played with it but thats it chances are though like LR or C1 the temp files if they are cache or scratch files will be quicker on a modern quick SSD and mainly cause of the access time more than the throughput
Click to expand...

NX uses cache. It speeds things up when I go back to my raw files, which I often do. In fact, I usually do a batch process on several hundred files before I cull my photos. So, the cache can get pretty large.

I don't really know the speed of the 2 internal drives I would use as a raid, only that they are 72000 drives and my system profile says they are ST3500641AS p with a 32 queque depth.
 
allan53 said:
Cache stays on the hard drive till it is cleared off. I think it is different than scratch as I think scratch gets deleted automatically.

I would want 60-80 gb for cache.

Thanks for the link. I still find it confusing as he talks about dual ssds. I know this would be better than a 2 drive raid, but I wonder if it would be faster if I only have 1 ssd.
Click to expand...

I see... PS does not use cache... Perhaps that's unique to NX? I use Aperture so I'm not familiar with the concept of cache... is that analogous to the storage of image previews? If so, I would endeavour to keep that on your SSD if possible. However, at 60-80GB, that sounds like it could use an SSD all on its own. If your photo library is really that big, you will likely either need more SSD storage space or have to use your mechanical drives... which is not a terrible option especially considering you already have them paid for. :)

Anyway, the last two rows in the chart I linked to compare a single SSD to a 4 drive mechanical array. Keep in mind that he's going to great lengths here to exaggerate the differences between the two storage mediums by using a ridiculously large scratch file.
 
allan53 said:
NX uses cache. It speeds things up when I go back to my raw files, which I often do. In fact, I usually do a batch process on several hundred files before I cull my photos. So, the cache can get pretty large.

I don't really know the speed of the 2 internal drives I would use as a raid, only that they are 72000 drives and my system profile says they are ST3500641AS p with a 32 queque depth.
Click to expand...

Don't use your boot SSD for scratch -- you want to avoid hammering the SSD like that in order to keep it from slowing down over time. If I were you, I'd RAID 0 the two 500 GB drives and use them for scratch (and other temporary stuff like downloads, etc.), because they are much more likely to fail than the 1TB disk, being *both* older and in a RAID 0.
 
Allan53 I did some extensive testing with Lightroom and cache and SSD

and found that at least with LR going to a raid 0 SSD was not really any faster than a single SSD for the cache ?

my main thinking is the files are not that big and when pulled off its more limited to the write time of a batch and or the program since we are editing one at a time on the screen ? a batch change does not need previews

the chart is this
attachment.php



while I know its LR ? it might have some relation to NX

might have to load up NX again to play with it ? but between Capture one and LR I am set
since I use Capture one also having the files on SSD has helped
 
I am curious as some say dont use SSD for scratch ? yet I know many who do in photography world ?

I keep hearing dont hammer them ? yet what is a SSD good for then ? are they really so delicate that they cant take being written to and read from ?

I am not sure if I am buying this or not

and not doubting you personally ? just the fact no real data to back anything up yet if they will fail quicker as scratch ? unless I missed that info :)

working more with my scratch on SSD every day ? I am thinking OWC is going to be getting some more money for the 40 gig and these will be purely scratch for both our machines and then two more for catalog and cache for LR

so end up with
boot 100 gig SSD
cache for LR two 40 gig SSD in raid 0 for catalogs and cache
scratch dedicated 40 gig SSD
 
Honumaui said:
I am curious as some say dont use SSD for scratch ? yet I know many who do in photography world ?

I keep hearing dont hammer them ? yet what is a SSD good for then ? are they really so delicate that they cant take being written to and read from ?

I am not sure if I am buying this or not

and not doubting you personally ? just the fact no real data to back anything up yet if they will fail quicker as scratch ? unless I missed that info :)

working more with my scratch on SSD every day ? I am thinking OWC is going to be getting some more money for the 40 gig and these will be purely scratch for both our machines and then two more for catalog and cache for LR

so end up with
boot 100 gig SSD
cache for LR two 40 gig SSD in raid 0 for catalogs and cache
scratch dedicated 40 gig SSD
Click to expand...

I will try the raid for my scratch/cache. At some point I will try the ssd drive. Like you, I think they are pretty solid. Maybe I should get another ssd drive?

Those are my thoughts - I don't have any answers. If I get another ssd it would just sit in my optical bay after I plug it in. Lloyd Chambers said that is safe with an ssd in a Mac Pro.
 
MLC NAND cells are good for 10,000 write cycles. That's for each cell. How that translates into real-world life expectancy is another matter as there are a lot of factors like write amplification and, of course, what's considered "typical" usage.

Intel rates their drives as follows:

The drive will have a minimum of 5 years of useful life under typical client workloads with up to 20 GB of host writes per day.
Click to expand...

I doubt my SSDs see more than 20MB of writes on average per day, but it really depends on what you do and how much of it.

I would highly recommend reading this page... http://www.anandtech.com/show/2614/4
 
Honumaui said:
I am curious as some say dont use SSD for scratch ? yet I know many who do in photography world ?

I keep hearing dont hammer them ? yet what is a SSD good for then ? are they really so delicate that they cant take being written to and read from

I am not sure if I am buying this or not

and not doubting you personally ? just the fact no real data to back anything up yet if they will fail quicker as scratch ? unless I missed that info :)

working more with my scratch on SSD every day ? I am thinking OWC is going to be getting some more money for the 40 gig and these will be purely scratch for both our machines and then two more for catalog and cache for LR

so end up with
boot 100 gig SSD
cache for LR two 40 gig SSD in raid 0 for catalogs and cache
scratch dedicated 40 gig SSD
Click to expand...
They're not suited for high write conditions, which scratch is. Given the current costs for SSD's, this means they're less likely to be considered "disposable", as this type of usage will mean they have to be replaced often. Say 1 - 1.5 years as a MTBR, and this may even be longer than the 40GB units can last (Mean Time Between Replacement). It all depends on your specific usage (affects the freqency each cell is written, aka write amplification).

In the case of LR, it's not the same as scratch (should last longer), and at a $100, a single 40GB unit per year may be acceptable (MTBR). Ultimately, that's up to the user to decide, but most keep looking at larger units, where the cost is more significant.

In your case, you're a guinea pig, as there's no long term test data to go from with SSD's (SSD makers are using empty drives and manipulating the statistics to get the published figures). So what ends up happening in your system would actually be useful information for those that want to do this (many want to, but indicate their budgets are too tight to replace SSD's that rapidly at existing prices <fastest models>). The 40GB or so capacity models may be acceptable, as $100 is an acceptable figure IMO (especially if the system's used for earning a living, which would have higher write volumes that hammer the SSD harder due to the expectation that the workload is higher than that of an enthusiast/hobbyist).

Just a thought. ;)
 
will be curious how SSD companies handle replacement and warranty issues ?
I can see a lot of companies turning down warranties and creating some bad will with people in the near future :) if they truly have issues that show up in the next year or two with a 3 year warranty ?


I think another 3 weeks and I will have a good handle on the SSD scratch thing :) and will be a guinea pig no problem $99 two bottles of decent 20 year tawny ?


part of me wonders also with paging files and OS since so many are using these for OS boot discs and paging can be heavy sometimes ? and back to the warranty ?

it is interesting time for sure and being on the bleeding edge of technology I always expect to be smacking myself and thinking I paid that much for that !!!!

if I had just bought apple stock instead of all my macs I would be a very rich man :)
I think of my first 128K mac and then the 512 and how much they cost compared to say what a car cost then :)

I know why they call it BLEEDING EDGE :)

I understand the 10k writes etc.. but maybe I should also say/ask or try to find out how much does a avg image use the scratch ? considering every time you open PS it sets a side a small amount of scratch how much is really used would be interesting to test when I get some time ;)

monitor the SSD over certain images etc...
 
VirtualRain said:
^^^ Then that's me on the left! :D
Click to expand...

see those red eyes !!! thats what 3 SSD in raid 0 will do to you folks !!!!!


almost posted this one but felt sorry for the little guy
220px-Guinea_pig_injection.jpg


but sometimes how I feel :)


but then again not as bad feeling as these little ones :)
guinea.jpg
 
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