SSD setup?

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SSD setup?

Postby tophee » Wed Oct 13, 2010 6:09 pm

Hello,

With the release of Ubuntu 10.10 I was considering an upgrade to one of those flashly and fast solid state hard drives.

I've done some reading and it seems there are a myriad of different things to do to get them to perform at their optimum. There is this TRIM thing (something to increase the life of the drive I believe) and does Ubuntu/Fedora etc include TRIM support with the latest kernal? What about caches? I've read that I should move cache to other drives or be held in memory. I've already got a 1Tb drive for my data. What about this 'alignment' thing. There is a lot of information and not much of: do A, followed by B, then C. I'm finding it quite confusing at the moment.

Whose tech is best for Linux? Someone advice would be greatly received and some instructions on how to set up one of these drives successfully.

I'm considering something like this: Option1, Option2, or Option 3.

(NB: No advertising that site, just happened to be where I was browsing before posting!)

Thanks in advance.

Chris
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Postby johnhudson » Wed Oct 13, 2010 7:25 pm

The main problem with SSDs is that journalling systems like Ext3 and 4 can accelerate wear; you really need to think about using something like btrfs if you are going to use it as a replacement for a traditional hard disk.
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Postby LeeNukes » Wed Oct 13, 2010 8:58 pm

You don't have to worry too much about wear and tear if its a proper SSD rather then the cheap flashbased device that was in the original EeePC.

You'll probably get 10+ years out of the HD easily using it normally. I doubt you'll be using it in 10+ years.

I'd recommend checking the speed though, write and read as they vary wildly from drive to drive. I'd hate for you to part with your money and find spending an extra £20-30 would have gotten you true SSD speeds.
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Postby nelz » Wed Oct 13, 2010 11:17 pm

The problem with a journal is that you are hitting the same part of the drive over and over, which is why it can break a standard flash device quite quickly. but SSDs use wear levelling so you are not writing to the same location all the time. Combined with the far higher quality of a proper SSD, this means you don't have to worry about flash wear in normal usage.

By the same token, it's also safe to put swap on an SSD.
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)
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Postby Dutch_Master » Wed Oct 13, 2010 11:29 pm

FYI: I've just put up a server, for LTSP purposes. I used an SSD for the system disk, the data disks are 2x WD 500GB disks in RAID 1. The thing boots in under 30 seconds, mainly limited by the Grub timeout and some services that need time starting. I used JFS for all partitions: if it's good enough for Big Blue, it'll most likely suffice for me too ;)
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Postby M0PHP » Thu Oct 14, 2010 8:04 am

AnandTech have some great articles about SSDs, and there really is more to them than just flash chips attached to a SATA cable.

I'd advise spending a bit of time getting some background information on what to look out for so you're more informed when making this crucial (pun intended) decision.

http://www.anandtech.com/show/2738
http://www.anandtech.com/show/2829
http://www.anandtech.com/show/3812/the- ... alssd-c300
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Postby tophee » Thu Oct 14, 2010 1:06 pm

Thanks for the replys guys.

Thank you for all the information and other considerations to take - that's exactly why I was asking for some help / advice as it seems to be a big subject.

Due to cost, I have limited myself to the more affordable end of the spectrum but the ones I linked to are (or so I thought) 'proper' SSDs.

@ johnhudson - that's exactly what I was concerned about!
However based on what Dutch_Master, Nelz and Lee are saying I shouldn't worry too much about wear with a proper SSD.
Rather I should just istall to the SSD drive and then put /home on my 1Tb drive.

Before I leap of the deep end, I think I will take the time to read the articals MOPHP linked to (cheers for those). I had a quick squint at them earlier and they certainly seem invaluble reference.

As I'm not planning on buying any hardware until the week after next (when I've some time), I'll use the time to do a bit of reading.

If anyone else can chip in with some real life recommendations, that'd be great.

Cheers

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Postby ollie » Thu Oct 14, 2010 1:21 pm

Another tip is to put the swap partition on the 1TB drive.
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Postby nelz » Thu Oct 14, 2010 2:14 pm

Surely swap is where you want the best performance when you have to use it?
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Postby Dutch_Master » Thu Oct 14, 2010 3:29 pm

It is Nelz. But in my particular case, although I have a swap partition, it's not likely to be used. For the light loads the server has to cope with, the 16 GB RAM should suffice, shouldn't it? ;) Besides, the swap is only a fraction of this size, if I'd have to use the standard rule (swap= 2x RAM) there wouldn't be space to install the OS anyway ;) (it's a 30 GB SSD :P) In retrospect, I might remove it altogether anyway...
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Postby nelz » Thu Oct 14, 2010 3:36 pm

That rule dates back to when 16MB was a more common amount of RAM. Although it is unlikely you will need to use swap, when you do you want it to be as fast as possible. You could set up as much as you can spare on the SSD and then another swap partition with a lower priority on the hard disk.

The idea that you shouldn't put swap on an SSD because "it might wear it out" is like buying a car then not driving it, for the same reason.
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Postby tophee » Thu Oct 14, 2010 6:01 pm

The SSD I was considering would be in the region of 40 - 60 Gb. I imagine for something like Ubuntu / fedora this would be more than enough space. As it's a desktop machine I think my 4Gb of ram should be enough, but a small swap space (roughly 12Gb) should suffice.
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Postby ollie » Fri Oct 15, 2010 12:08 pm

These days the primary use of swap on desktop/laptops is when they hibernate or suspend. This means you need a swap at least as big as your RAM + some extra, so it comes back to 2 x RAM again :wink:

The reason I was recommending to put swap on the second 1TB drive is because of the relative small size of SSDs and the relative speed throughput of a swap partition at the start of a large drive (lower seek times). Wear levelling on the better quality SSDs shouldn't result in any impact over the life expectancy of a server - 3 to 5 years whilst under warranty.
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Postby M0PHP » Fri Oct 15, 2010 2:01 pm

ollie: I didn't think hibernate/suspend worked on Linux anyway? ;)
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Postby Rhakios » Fri Oct 15, 2010 6:57 pm

Personally I don't bother with hibernate, I just use sleep or switch the thing off. Booting from hibernate actually seems slower than cold booting.
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