Four Tweaks for Using Linux with Solid State Drives

Tombuntu ^ | September 4th, 2008 | Tom

[Ernest_at_the_Beach]

SSDs (solid state drives) are great. They’re shock resistant, consume less power, produce less heat, and have very fast seek times. If you have a computer with an SSD, such as an Eee PC, there are some tweaks you can make to increase performance and extend the life of the disk.

1. The simplest tweak is to mount volumes using the noatime option. By default Linux will write the last accessed time attribute to files. This can reduce the life of your SSD by causing a lot of writes. The noatime mount option turns this off.

   Open your fstab file:
   sudo gedit /etc/fstab

   Ubuntu uses the relatime option by default. For your SSD partitions (formatted as ext3), replace relatime with noatime in fstab. Reboot for the changes to take effect.

2. Using a ramdisk instead of the SSD to store temporary files will speed things up, but will cost you a few megabytes of RAM.

   Open your fstab file:
   sudo gedit /etc/fstab

   Add this line to fstab to mount /tmp (temporary files) as tmpfs (temporary file system):
   

   tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0

   Reboot for the changes to take effect. Running df, you should see a new line with /tmp mounted on tmpfs:
   tmpfs 513472 30320 483152 6% /tmp

[Ernest_at_the_Beach]

Not sure how this works if you only have an SSD...

[ShadowAce]

[bvw]

Hmm ... I didn’t realize that modern SSDs still suffered the life-limited writes.

[Ernest_at_the_Beach]

Found this link in the commentary:

SSD Myths and Legends - "write endurance"

[Ernest_at_the_Beach]

Link at post #5 is to a Texas Memory Systems company which makes special stuff for enterprise servers.

[Ernest_at_the_Beach]

Further discussion from website at #5:

Are MLC SSDs Ever Safe in Enterprise Apps?

******************************EXCERPT****************************

SLC versus MLC in Enterprise SSD arrays - by Zsolt Kerekes, editor, June 2008

The original purpose of my SSD Myths article was to show that you needn't worry about wear-out if you use "best of breed" flash SSDs with write-endurance on the order of 1 million cycles and above.

When it was first published (in March 2007) all flash SSDs in traditional hard disk form factors used SLC.

But in the year following publication many leading SSD oems (including Samsung, Mtron and STEC ) have also introduced MLC products too.

To confuse things even more - in June 2008 - Silicon Motion announced a new family of flash SSD controllers which enable oems to mix and match MLC and SLC chips in the same drive - creating in effect SLC-MLC hybrid SSDs.

MLC doubles the capacity of flash memory by interpreting 4 digital states in the signal stored in a single cell - instead of the traditional (binary) 2 digital states.

This technique has been commercialized and proven over many years in hundreds of millions of cell phones and MP3 / iPod music players - where the theoretical consequence of data corruption (if anything went wrong with this risky "new" storage technology) was no more serious than an inaudible sub millisecond sound blip or invisible pixel splat.

In the SSD market MLC yields much lower cost storage than SLC with read / write speeds which are nearly as fast as the best SLC devices.

The manufacturers of first generation "hard disk replacement" MLC flash SSDs have responsibly classified them as aimed at the "notebook market" and by subtle wording differentiated them from their more pricey "enterprise" products. In the low duty cycle world of a notebook these MLC SSDs should give a good operating life - typically similar to the hard disks they replace. (Most SSD marketers would claim their MTBFs are even better than HDDs).

But there's no way to tell the difference between SLC and MLC SSDs externally (apart from the model numbers). Put them in a rackmount system in a datacenter with fast processors which can pump them continuously close to the maximum speed and what happens?

[Ernest_at_the_Beach]

I think the answer is yes....after scanning thru the last article...and there are links for further reading....

Now for non enterprise usage ( netbooks) ,..maybe not a problem.

[jeffc]

Maybe I'm looking in all the wrong places, but the data I've seen is that SSD's are not as fast as spinning disk drives (SDD's).
I would think that by their very nature, seek-time would be dramatically reduced on SSD's. SSD's would be much prefereable as there are no moving parts to wear out, no head crashes, smaller footprint, consume less wattage, etc. You could probably even make them hot swappable (ala USB thumb-drives, except as a direct plugin to the HD bus, not onto the USB).

So what is it? Bus-speed? If so, why would SSD's have less bus bandwidth than an SDD?

[steve86]

The comments under that article are worth reading — some good insights about file systems.

[bvw]

Log files are a problem. Directories will be a problem unless you turn off access timestamps, and directories that contain temp files will continue to be problem — such as browser temp files. Can alleviate with judicious combination of ram disks, or inside the SSD hardware via tricks, but eventually the SSD — if flash — will fail.

[ShadowAce]

It’s the non-volatile nature of the SSD that slows it down.

[Ernest_at_the_Beach]

Found this:

SSD vs. SATA RAID: A performance benchmark

*****************************EXCERPT***************************

The random seeks were about 6,200/second for ext3 and 3,800/second for XFS on the SSD. To put this into perspective, the graph shown below contains the seek performance for the SSD, a single 750GB SATA drive, and six 750GB SATA drives in RAID-6. Notice that having six hard disks does improve seek performance noticeably over a single hard disk, but the single SSD still dominates the graph. This advantage in seek time explains why systems equipped with a SSD drive can boot significantly faster than those without. Booting a machine or loading a complex application normally calls for thousands of files to be read, and these are normally scattered over a disk platter, causing many seeks. Because the SSD has such an advantage in seek time, it can show with an overall improvement measured in seconds to load a very large application. Bonnie seeks

The final graph shows the block read, write and rewrite performance of the SSD against a single 750GB disk and a RAID-6 of six 750GB SATA drives. There isn't a great deal of difference between the block transfer performance of a single 750GB SATA drive and the SSD. The RAID-6 of 750GB conventional hard drives is significantly faster across the board. Bonnie vs RAID block IO

The point of the previous comparison on block transfer is to show the gap between the block IO performance you would get if you spent the same money on conventional hard drives instead of the SSD. The SSD has a dominating advantage in seek time, yet its overall capacity is a slight fraction of what you can get by buying conventional hard drives, and hard drives in RAID dominate the SSD in terms of block transfer speeds.

[martin_fierro]

Had a really good experience installing Ubuntu ("Easy Peasy") on the EEE 701 from a flash drive.

I think the version is still Intrepid, not Jaunty.

[bmwcyle]

bttt

[Ernest_at_the_Beach]

looks good.

[zeugma]

BFL. Like the ram disk /tmp thing. Would make it operate more like Solaris boxes.

[jeffc]

Thanks. I was assuming (correctly, I think) that SSD seek-time would help it beat anything the SDD (Spinning Disk Drive) would have over and SSD.
With faster seek-times couldn't an SSD use smaller cache and pre-fetch and smaller block transfer sizes, making it even faster?
This would mean you wouldn't need as big a bus and could speed up transfer times even more, right? Or are bits leaking out of my head onto the floor (wouldn't be the first time, LOL!)?

[jeffc]

It’s the non-volatile nature of the SSD that slows it down

You're referring to writing to the drive, though, right? Burning it into the cells to get the data to "stay"?
How would that affect reading/retrieval? I was hoping that the overall speed would increase from SDD to SSD.

[Marie Antoinette]

FYI! I know you like that little machine. :)