Linked by Thom Holwerda on Thu 27th Sep 2012 19:36 UTC
Apple I bought a brand new iMac on Tuesday. I'm pretty sure this will come as a surprise to some, so I figured I might as well offer some background information about this choice - maybe it'll help other people who are also pondering what to buy as their next computer.
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WereCatf
Member since:
2006-02-15

But I have to admit that I don't trust SSDs for the long term--even when used as a system drive.


A regular consumer-oriented SSD should last around 10 years as a system drive just fine, even with swap on it. There are several websites about this, including specific burn-in benchmarks that just keep reading/writing the SSD until it goes bust.

Modern computers and hard drives are so damn fast anyway, I honestly can't imagine an SSD being that big of an improvement over a good quality hard drive


The difference is like a night and day. SSDs especially excel at reading small files and/or fragments that are scattered all over the disk because of the miniscule seek times. Out of curiosity I tested my regular HDDs the other day and got 7ms and 9ms seek times whereas a USB 3.0 stick got 0.05ms seek times. That's 140 times faster. And guess what? Typical OS-files and program libraries and binaries tend to be small files, scattered all over the place.

Regular HDDs are still good for sequential data, but even there SSDs these days trump HDDs in speeds, with some going up to 500MB/s sustained sequential write speeds.

Reply Parent Score: 3

UltraZelda64 Member since:
2006-12-05

Well, two things. First, I'm not sure I can believe that "10 years" figure; I've done some reading about SSDs, and it doesn't seem totally believable to me. Not for a system drive with swap and all your data, at least. It just sounds too far-fetched. Maybe in a perfect world and in perfect conditions, but not in this world.

And second, SSDs definitely have the theoretical edge over hard drives when it comes to the speed of reading files that are laid out non-contiguously on the drive. But... at the same time, in all my time running Linux (exclusively for about 6 years), I have not had any major slowdowns due to fragmentation. It just doesn't happen. I was leery about moving entirely to an OS that doesn't even offer a native defragmentation program, but it turns out that it really is needed much less.

On the other hand, before I switched I was using Windows XP, and it seemed like I was running PerfectDisk every week or two just to keep the drive running at peak speed (especially the system drive). So... I guess the moral of the story here is that Windows users have more to gain in terms of performance than Linux users by using an SSD?

I recently found out about the free version of PerfectDisk and had my cousin install it on his Windows 7-based machine... as I expected, just one offline/boot defrag and one online defrag made a very noticeable performance improvement. So apparently on Windows a good defragging is still needed. [Note: Previously, I told him to install the free program Defraggler, which he used until then. IMO, PerfectDisk is a must... if I ran Windows today, I would no doubt buy another license for a recent version of the program.]

Reply Parent Score: 1

Luminair Member since:
2007-03-30

the parts about ssd speed and lifetime sound right to me. even on fast new systems, hard drives still thrash left and right when doing lots of stuff.

and think of how many old semiconductors there are still working. the 10 year estimate makes sense because most ssds won't get worn out enough to kill the NAND. most of the stuff on an ssd just sits there. and when stuff is written, it is spread out across the nand to reduce aging.

Reply Parent Score: 2

WereCatf Member since:
2006-02-15

And second, SSDs definitely have the theoretical edge over hard drives when it comes to the speed of reading files that are laid out non-contiguously on the drive. But... at the same time, in all my time running Linux (exclusively for about 6 years), I have not had any major slowdowns due to fragmentation.


Don't try to turn this into an anti-Windows argument. You know perfectly well that both Windows and any average Linux-distro consists of thousands of small files. It doesn't matter whether those files are fragmented or not, they're still not laid out on the disk in such an order that the drive can read every single one of them in sequential order and that is exactly why low seek times matter.

Also, as I said these days SSDs trump HDDs even in sequential speeds. Check out e.g. http://thessdreview.com/our-reviews/adata-xpg-sx300-256gb-msata-ssd... : the SSD can write ~200MB/s incompressible data in sequential order, something that no consumer-oriented HDD can do.

Reading both https://en.wikipedia.org/wiki/Solid-state_drive#Comparison_of_SSD_wi... and http://thessdreview.com/ would do you a lot of good.

Reply Parent Score: 3

Alfman Member since:
2011-01-28

UltraZelda64,

"First, I'm not sure I can believe that "10 years" figure;"

I've read that manufacturers are targeting 3 years of heavy use. Anything less than that they consider unacceptable. Anything more they consider as an opportunity to increase the tradeoff from reliability to capacity. However all these reliability figures are based on "typical" writing patterns as they're handled by the wear-leveling controller. If you are going to regularly re-write the entire flash, then the wear-leveling algorithm becomes irrelevant and your back to the NAND chip's underlying program/erase lifespan (spec'd around 3-5K).

So, whether flash is acceptable depends upon the application. If you are a photographer, you can fill up your flash card a few thousand times before going over the manufacturer's specs. This is acceptable to most consumers.

Storing swap could be ok, but only if you don't expect applications to leak into swap very often. If an application enters a period of vicious swapping such that the entire swap area is being rewritten continuously (and assuming the swap space is a large fraction of the SSD capacity), then you're looking at depleting the NAND chip's lifespan very quickly.

Flash is much better suited in scenarios where reading is much more frequent than writing, which is usually the case for operating system files. Just be aware of processes that continuosly write to flash.

Reply Parent Score: 2