Are SSDs really worth it?

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RAMbo
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Are SSDs really worth it?

Post by RAMbo »

SSDs are much faster than regular HDs. They are more expensive per GB as regular HDs but that depends greatly on the quality of the SSD and HDs.
What bothers me with SSDs is their durability.
The cells of a SSD can be wiped/written a limited number of times. The manufacturers found all sorts of tricks around that to improve things greatly. But still it doesn't look good.
I used this free tool to measure my disk usage. http://www.hyperio.com/hIOmon/hIOmonBigPicture.htm
First it shows the queue depth isn't that high on a typical workstation. Neither are the IOs.
Lifespan depends greatly on the amount of data used daily. Typical calculations are 10GB day. I'm way above that.
I have a few programs that are very heavy on my HD. They use a LOT of temp files that only exist for only a few minutes.

Samsung is currently speeding up their SSDs by adding software that allows the user to set up to 1GB of RAM as cache. That looks a bit like what PrimoCache does.

So all that combined I'm wondering that buying a good speedy regular HD plus a few GB extra RAM dedicated to PrimoCache/RAMdisk might be a better solution.
Sure SSDs are much faster when writing huge files. But when using hIOmon it shows the vast majority of disk activity is 4k blocks.
When PrimoCache handles those blocks correctly with a huge buffer things would be great.

Even better would be if I could configure that certain directories never must be written to HD. They contain temp files that have to be redone anyway when the system crashes.

My only concern is the CPU load the Primo products cause...

Any idea's????
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RAMbo
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Re: Are SSDs really worth it?

Post by RAMbo »

Additional question for Romex: What is the maximum amount of cache you advise?
dustyny
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Re: Are SSDs really worth it?

Post by dustyny »

The short answer is SSDs are indeed that useful you should get one or two (I have 8xSSDs in my rig) :D
The cells of a SSD can be wiped/written a limited number of times.
Which is far more then what you'd use in a normal desktop setting. This idea that SSDs would fail due to memory cell failure never actually became a thing, it's an urban legend. I've explained why in the posts that I made in the FancyCache section.
First it shows the queue depth isn't that high on a typical workstation. Neither are the IOs.
Queue depth is only one factor and unless you are on a server chances are you'll never see a long queue depth. The low latency is what gives SSD their major advantage. Along with the much higher transfer rates, there really is no comparing.
Samsung is currently speeding up their SSDs by adding software that allows the user to set up to 1GB of RAM as cache. That looks a bit like what PrimoCache does.
Yes just about all the major drive manufactures have their own caching solution.
So all that combined I'm wondering that buying a good speedy regular HD plus a few GB extra RAM dedicated to PrimoCache/RAMdisk might be a better solution.
No you'll still have a problem on your writes, unless you turn on write delay which puts your data at risk. I've lost a number of VMware virtual machines using write delay. This feature is really only useful for a limited amount of use cases (temp data). As always a backup of critical data (stuff you dont want to lose) is 100% necessary...
Even better would be if I could configure that certain directories never must be written to HD.
Perfect example of what can benefit from write caching. Create a 2nd partition on the drive and create a seperate cache for it using primo disk. Be warned though unless you're using lots of temp data (CGI rendering, data processing, etc) you won't really benefit all that much.
My only concern is the CPU load the Primo products cause...
Unless you have an older PC, the load shouldn't even register on the CPUs. I have a 6 core Intel Core i7, with the OS, 3 virtual machines, a few apps (browser) and primocache, I'm still not at 1% usage.
What is the maximum amount of cache you advise?
For read as much as you can dedicate without starving the apps you need to use. I use 64GB on one server and 8GB on my workstation. For write, I'd point you to what I wrote above, it's dangerous to use (though it's rarely a problem) so if you have situation where you have an app that is truly bottlenecked on the write (as in a CGI render, code compilation, data processing) then give it as much as you can spare. For all other uses all you're doing is putting your data at risk and hiding the progress bar, the data is still being written to the drive at the same speed.
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RAMbo
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Re: Are SSDs really worth it?

Post by RAMbo »

Found a nice life span test: http://us.hardware.info/reviews/4178/ha ... conclusion
No you'll still have a problem on your writes, unless you turn on write delay which puts your data at risk.
I can't even remember when I had a crash. Most of my data will be useless anyway after a crash. The majority of my disk access is stuff like downloading and video rendering. So if the machine crashes I just as well may have no file as a partially saved file. The other major use is read only access. I'm well aware there are processes that write to HD. It would be best I could isolate them to a different drive without write delay.

It's possible, perhaps even likely, I will have problems with my writes but that depends on how much writing is going on. If there are say 50MB bursts with 30 secs between my HDs could catch up.

Dataloss in general isn't usually a big problem for me. All my stuff is backed up daily and certain directories hourly. My windows install is imaged.
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Re: Are SSDs really worth it?

Post by InquiringMind »

RAMbo wrote:Found a nice life span test: http://us.hardware.info/reviews/4178/ha ... conclusion
I recently had two (Hitachi) 1TB drives start failing (SMART reporting re-assigned sectors) at the same time after very light use, while I've yet to encounter anything with my 6-(Samsung)-SSD RAID array used for main storage. From that perspective, it's the hard disks that seem to have the lifespan problems and if some of the design ideas planned (filling them with helium, which will leak out over the next couple of years) go ahead, they may become less reliable still.

Given SSD's performance advantages (particularly with small files) and more rapidly falling cost/GB, it won't be long before everyone is asking whether hard disks are really worth it. ;)
dustyny
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Re: Are SSDs really worth it?

Post by dustyny »

Given SSD's performance advantages (particularly with small files) and more rapidly falling cost/GB, it won't be long before everyone is asking whether hard disks are really worth it. ;)
Especially as the general public turns more to streaming over downloading. It's pretty hard for the avergage user to fill a few hundred gigs if their not downloading media.
docbill
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Re: Are SSDs really worth it?

Post by docbill »

I swear by them. The real question is not if SSD's are worth it, but what is the best way to use them. So far the most reliable way to use them seems to be just as a normal drive. Buy one big enough, and make it your boot drive. Even if you bios does not support directly booting to the SSD, you can always use grub to do a staged boot from the SSD.

Caching seems like a less effective use. Given the stability issues I've run into with primo-cache I would not recommend using it to cache your boot drive. Even if it worked 100% problem free, that introduces one additional to consider anytime anything else causes an issue. Primo-cache seems to work well for non-primary drives though. Given the expense of a large SSD, it seems like a good alternative to a hybrid drive.

Speaking of which I also recommend the hybrid drives. If for example you have a laptop with only one drive slot, and you have a TB of games then you probably are not going to be able to use an SSD. But the hybrid drives still will give you some of that performance boost you are looking for. In general, it won't speed-up most games, because there is to little solid state memory for that. However, it will significantly decrease your boot times, time to start-up Steam, and other common applications. I just recently bought my son a $400 laptop for his birthday. The first thing I did was remove the hard drive and clone it to a hybrid drive. The laptop now performs about the same as my $2000 work laptop for productive tasks. The other advantage of hybrid drives is they are OS independent. You can't use primo-cache on Fedora, but using a hybrid drive for Fedora does give me a noticeable boost. But then the down side is the hybrid drives do not have enough solid state memory to cache more than one OS at a time. So if I used Fedora regularly, my Windows performance will suck. If I use Windows regularly, then my Fedora performance will suck.

Now, one thing I've been wondering about is how well a solution like primo-cache would work with a USB3 stick... Clearly it will not be nearly as good as with an SSD, but it might still give a respectable performance boost and increase laptop battery life.

Bill
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Re: Are SSDs really worth it?

Post by msulliva »

You bring up a question I've been wondering about, namely using PrimoCache with an SSD and a large non-primary HDD instead of buying a hybrid HDD. I have a SSD as my system drive, but I've been thinking about using a different SSD along with an HDD used for games and other applications. What advantages or disadvantages does this have compared to a dedicated hybrid HDD?
docbill
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Re: Are SSDs really worth it?

Post by docbill »

I imagine the benefits of hybrid vs ssd and cache software is going to depend on your use case. But of course there are the generic considerations:

Hybrid Drive:
+ Nothing additional to buy.
+ Easy. Plug in and use.
+ Very safe write caching. (e.g. No chance of losing data in solid state memory, do to an improper shutdown or such.)
+ OS independent
- No ability to tweak for your needs.
- Very small amount of solid state memory that can not be increased.
- The hybrid drives on the market are 5400 rpm, not 7200 rpm. (The older ones were 7200 rpm, but had a high failure rate.)

Whether either makes sense at is where we get into use cases. For example, I use my data drive mostly for torrents. I took a 18 GB partition I had allocated on my SSD for Fedora and reallocated it for primo-cache. So far my tests indicate the hit rate of primo-cache is directly proportional to the size of torrent I'm sharing. For example, if I am seeding a 120 GB of torrent, the data is pretty much randomly accessed. So there is no optimization primo-cache can make on which blocks it caches. So primo-cache will end-up caching a random 18 GB portion of the share, giving me a cache hit ratio of 15%. I can't really think of a way that is useful for me... On the other hand what is useful, is lets say I'm seeding a 12 GB torrent. After awhile of sharing, primo-cache will have 100% of the file in the L2 cache. That means if I come along and start using doing something else, say copying more files to and from the hard drive, or maybe playing videos off the hard drive, etc I will effectively get the same performance as if I were to stop the seeding while I was doing these things. That to me is a noticeable advantage of using caching software. A hybrid drive would pretty much do the same thing, but with the advantages and disadvantages listed above.
RobF
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Re: Are SSDs really worth it?

Post by RobF »

docbill wrote: Caching seems like a less effective use. Given the stability issues I've run into with primo-cache I would not recommend using it to cache your boot drive.

Bill
Bill can you elaborate on this please?
I'm one of the new guys on the primo-cache block and am interested in your experiences with stability as referenced in your post.

Were you using deferred writes when you encountered the "issues"?
I'm not sure why you wouldn't cache a boot drive but you would cache a data drive.

I think extra RAM and a caching drive is a superior and cost-effective solution but if money is no object then I can see going all in for SSD.

Regarding your comments about LINUX disk cache. We've had proper caching for a long time in LINUX so there is no need for primo-cache on that platform from my experience. Here is a decent write up on the linux caching facility.
http://www.westnet.com/~gsmith/content/ ... dflush.htm

Thanks,
Rob.
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