Author Topic: SSD in core  (Read 1931 times)

bongowongo

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SSD in core
« on: April 03, 2011, 10:05:27 am »
Is it smart to use an SSD as a HD in the core. the 60-80gb are becoming more and more affordable.
Media will be on a NAS. So will SSD survice the IO of linuxmce? Is it a big benefit in speed? I am under the impression that you should avoid SSD of you have a lot of "write" actions on that HD.
Is trim working in Linux/LinuxMCE?

klovell

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Re: SSD in core
« Reply #1 on: April 03, 2011, 05:25:36 pm »
I have not heard argument about ssd in high write applications.  I put one in my core and it seems to me that the core and my mds boot faster.  The last time I researched the topic, which was a while ago, linux wasn't able to unleash the true performance capabilities of a ssd.  It would still be faster than a conventional hd but no where near as fast as the same ssd running windows.   I didn't do it so much for speed, I was after the reliability.  Typically they out last conventional hard drives.

theteju

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Re: SSD in core
« Reply #2 on: April 03, 2011, 08:18:40 pm »
I am also looking to invest in SSD.

My observation is if you dedicate a hard drive for system files only, and NO media at all, the installation hardly uses 40 gb at the max.

So, my question is will 50 gb be enough for core? ( I know recommended is 80gb) just curious.

thanks in advance.

JoakimL

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Re: SSD in core
« Reply #3 on: April 03, 2011, 08:32:53 pm »
SSDs do indeed have an issue with write operations, since there's a finite limit on how many writes a NAND memory cell will survive. SSD controllers take this into account in two ways 1) block remapping, the block ids the operating system sees is only a logical block number that will be changed on every write and 2) there's (lots of) spare memory blocks which kick in as soon as the SSD controller is identifying extensive wear in a memory block.
So in reality even hi write scenarios will take many years to wear out a SSD drive.

JoakimL

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Re: SSD in core
« Reply #4 on: April 03, 2011, 08:36:01 pm »
And the size question: on my last install I checked disk usage right after it was completed and for me it was just over 8 GB. This is with Mythtv, Squeezeserver and Tellstick support installed and configured. I haven't checked how large it is now, I have loads of media and LMCE source files installed.

JoakimL

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Re: SSD in core
« Reply #5 on: April 03, 2011, 08:44:00 pm »
Third in a row... You ought to be able to cut down on the writing a bit. I know you can increase logging by LMCE and there's 5-6 log levels active by default which (if you dare) can be taken away. The second thing causing lots of writes ought to be the DCErouter (please correct if I'm wrong). This is a design issue, but since very few commands in LMCE need true persistence it should be possible to get away with these as well. If this is a simple configuration change or if it requires (extensive) source code changes I cannot tell.
Third area would be all the products involved where you could look at changing settings for logging and other writes. This would vary by product.

bongowongo

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Re: SSD in core
« Reply #6 on: April 03, 2011, 08:51:11 pm »
And how do you trim the disk?

JoakimL

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Re: SSD in core
« Reply #7 on: April 03, 2011, 09:00:06 pm »
What do you mean with trim in this case (trim as in SSD trim command?)?

bongowongo

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Re: SSD in core
« Reply #8 on: April 03, 2011, 09:26:07 pm »
yes

JoakimL

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Re: SSD in core
« Reply #9 on: April 03, 2011, 10:06:53 pm »
We just wait for kernel 2.6.33...
Since Ubuntu 10.04 comes with 2.6.32-25.45 it means some more time waiting. ;-)

theteju

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Re: SSD in core
« Reply #10 on: April 06, 2011, 05:41:46 pm »
I am even more confused with the answers here, in short,, is SSD good for a core or not??

klovell

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Re: SSD in core
« Reply #11 on: April 06, 2011, 06:32:38 pm »
I am even more confused with the answers here, in short,, is SSD good for a core or not??

Well there'll always be someone saying it's a bad idea.  I have 5 physical personal servers at my house, that are running 24/7, and 4 out of 5 of them (which includes my core) has SSD installed. 3 out of the 4 has had a SSD for well over 2 year now and I have not had any problems.  I think I installed the SSD in my core about a year ago. 

Here's the pro's:
  • less power consumption
  • Faster - although you wont see the max performance capabilities of the drive it's still faster than a spinning disk.
  • generally they are more reliable since there are no moving parts that will fail
  • Cheaper and more reliable than a Raid 5 (reliability is debatable)

Con's
  • I did a quick search and just like a usb sticks they have a shelf life in regards to writing to it. Although they use higher quality chips so they will last you long enough to make it worth it.
  • Drive size will be much smaller
  • Drive space per MB is substantially more expensive. 
  • Not as fast as a raid 5
Someone add to this if I missed something. 

I definitely saw a decrease in the time it took to regen and boot, both md's and my core.  Especially after a reboot where all 4 md's are booting at once.  Keep in mind that i have a full gigabit network with two PowerConnect 2848 as my backbone.  The hard drives are truly my bottle necks on my network.

phenigma

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Re: SSD in core
« Reply #12 on: May 07, 2011, 06:55:20 pm »
I have to add one more SSD Pro:
   Quiet - the SSD is completely silent in the HTPC case in my living room

klanmce

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Re: SSD in core
« Reply #13 on: May 10, 2011, 11:08:00 pm »
If SSD cost is prohibitive and want a slight improvement.

I replaced the desktop drive with a WD RE4 (500 GB) in my core early this year, resulting in an improvement in Orbiter regen time and MD startup; really did not have the SSD money.

Have three (3) Web Orbiter(version 2), four (4) MD's, a WebDT and a desktop installed Orbiter.

Of course not quieter or more efficient.

hari

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Re: SSD in core
« Reply #14 on: May 11, 2011, 08:09:39 am »
For trim to work the filesystem needs to support discard, and it needs to be enabled as mount option
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