[Tfug] SSD plans & disk usage

[Louis Taber]

Hi All,

My plan is to use the SSD as the root device and /usr to help system
performance.   I have two 640GByte drives that I am planning on mirroring
the rest of the system with and a 250GByte drive for "secondary" backup.
/var, & /home  will definitely not be on the SSD drive.  My plan is to use
the SSD for booting and executable binary  to speed up the overall system.
On my current system / and /usr total 9.704GBytes.

The amount of activity on the my log device should be low enough that
placing /var on a SSD would make little difference.
In the last 11 hours my system has written 54 lines totaling 3626 bytes to
/var/log/syslog --  54 writes in 11 hours.

Has anyone seen any statistics, or know how to acquire them easily on
various partitions to see if my plan will result in any obvious improvement
in system performance?  (Is the kernel keeping track of reads and writes by
partition?)  It might just be a waste of money <sigh>.

BTW: My first personal disk system cost $1500 or so.  It was two 8 inch
floppy drives, controller, power supply, box.  256K Bytes each (If I
remember correctly.)  The spindle drive motors were 120VAC motors.  The
drives were $500 each,  the controller card, as a kit about $300,   and
external box and power supply made up the rest.  I was at IBM at the time I
made the purchase.  The date must be about 1979-1980.  I was the first IBM
employee to request and get the employee discount on fifty 8 inch floppy
disks, which probably cost me about as much as I will spend on the SSD!
Things have changed.

  - Louis

On Sat, Jan 15, 2011 at 3:21 PM, Tom Rini <trini at kernel.crashing.org> wrote:

> On Sat, Jan 15, 2011 at 2:13 PM, Christopher P Robbins
> <robbinsc at gmail.com> wrote:
> > On Jan 15, 2011, at 1:05 PM, Tom Rini <trini at kernel.crashing.org> wrote:
> >
> >> On Sat, Jan 15, 2011 at 12:15 PM, Harry McGregor <micros at osef.org>
> wrote:
> >>
> >>> I would recommend buying 20-30% more SSD then you think you will use,
> as it helps the wear leveling algorithms.
> >>
> >> And if you go that route, don't forget to start mounting various
> >> things as tmpfs and think about what logs you really care about, for
> >> how long (and tools like logwatch can be good here too).
> >
> > Is there a "best practice" for mixing storage (ie - SSD with larger SATA
> drives)?  Would it be best to drop /var/log on SSD and keep media on the
> SATA?
>
> To me, it depends on your application.  What I'm doing (and got me
> digging here) is usb stick rootfs on a desktop turned NAS.
>
> For the longest time I've been using logwatch to see if there's
> anything I care about going on and short of an easily reproducible
> system crasher, I don't care if I have logs for forever.  So I shoved
> /var/log onto tmpfs, made logrotate compress and not keep things for
> too long (and rc.local mkdir /var/log/{apt,samba}).  I also took a
> look at what I do have running and made stuff that's writing/deleting
> cache/log files I don't care about use /tmp, which is also a tmpfs.
>
> That's not to say you can't keep /var/log and so on on the SSD and not
> have it still have a rather reasonable life span.  But it does make
> you question what you really care about.  Further, if you do really
> care about logs, a coworker of mine setup something similar to what I
> have except it plays fancy games to move the logging over to the RAID
> once it's up.
>
> --
> Tom
>
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