Investigation: Is Your SSD More Reliable Than A Hard Drive? • Hacker News Board

Re: Investigation: Is Your SSD More Reliable Than A Hard Drive?

#51

Post by caf » Tue, Sep 20, 2011, 5:56 AM UTC

caf wrote: post #10

AngryParsley wrote: post #2

One thing the article didn't address is performance over time. Even with TRIM support, SSDs get slower as they're used. Occasionally, cells die prematurely causing spare capacity to decrease. This won't affect read speeds much but it will hurt writes. These older SSDs will still be faster than hard drives but they won't be as fast as you'd expect them to be. Now for some of my own data. Here's an Intel X25-M G2 after…

The kernel should really issue a large TRIM for most of the swap partition at swapon time.

...and in fact, it does so: http://lxr.linux.no/#linux+v3.0/mm/swapfile.c#L2117 (and has since kernel 2.6.29).

Additionally, if you set the SWAP_FLAG_DISCARD flag to swapon(2), it'll issue TRIMs for swap space that is freed at runtime. You'll need a pretty recent /sbin/swapon to support that flag, though.

Re: Investigation: Is Your SSD More Reliable Than A Hard Drive?

#52

Post by caf » Tue, Sep 20, 2011, 6:01 AM UTC

lloeki wrote: post #45

nordsieck wrote: post #40

Earlier quoted context omitted.

Once upon a time, it was best practice to keep the swap file/partition (or log files, etc.) off of the SSD in order to keep the frequent writes from wearing out the SSD too quickly. Do you feel like this is outdated advice?

Certainly putting the swap not as a partition but as a file on the filesystem will help with TRIM and maybe even wear leveling.

It won't make a difference - in both cases, the swap code accesses the underlying block device directly, and is responsible for TRIM. (The swap code does issue TRIMs though, since kernel 2.6.29).

Re: Investigation: Is Your SSD More Reliable Than A Hard Drive?

#53

Post by wglb » Wed, Sep 21, 2011, 12:56 PM UTC

r00fus wrote: post #44

wglb wrote: post #24

Earlier quoted context omitted.

I disagree. In my collection of always-on 30 machines in my basement, over the last three years I have had probably 10 power supplies die, and only two hard drives. The hard drives that died--two 500 gig drives--died in the same month after just two years. I don't keep spare hard drives, but i do keep spare power supplies.

Interesting anecdote. I would argue that your always-on machines are not similar to an average PC/laptop. Perhaps your situation is more analogous to servers (most mid-high end servers come with redundant power supplies).

In the last enterprise environment I worked at, users were asked to leave their machines always, largely for software delivery and other updates,

Probably what is different about my setup is that my cpu meters mostly run at 100%.