[Soekris] Poor I/O performance

Karsten Kruse karsten.kruse at qits.de
Wed Mar 12 11:28:20 CET 2014



Am 12.03.2014 10:37, schrieb Bob Bishop:

> If your software doesn't support TRIM then SSD write performance (and read, to a lesser extent) will start to suck once the disk has had a certain amount of use.

Right!

During initial installation i made an image. First i filled the empty
space with zeros:

for i in $(seq 100) ; do
  dd if=/dev/zero of=/$i.dd bs=1M count=1024
done

The idea was to not have empty space with junk data in it, because that
would not compress very good. Then i made the image:

dd if=/dev/sda bs=10M | gzip --fast | ssh -c arcfour
kkruse at nb8810.qitsloc.ratq.local "cat > /home/kkruse/img.dd.gz"

The result was a 900 mb file. The command to write it back:

ssh -c arcfour kkruse at nb8810.qitsloc.ratq.local "cat
/home/kkruse/img.dd.gz" | gzip --decompress | dd of=/dev/sda

This is a SSD nightmare, i guess. ;)

I just used fstrim to tell the SSD that almost all of it is empty space,
for the future i added the discard mount option.

The write performance went from 20 MB/s to 30 MB/s. Not perfect, but at
least a bit better.

MFG,

Karsten Kruse


-- 
Karsten Kruse
System Engineer Unix/Linux
Operation Center Infrastructure

Telefon: +49 (0) 2102 - 852 - 4335 (- 202 Fax)
Karsten.Kruse at qits.de
http://www.qits.de/

QITS GmbH, Halskestraße 11-15 - 40880 Ratingen
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