Hardware RAID1 and SSD - poor performance?

Question

linux

What we have:

• 2x Intel 520 180GB (SSDSC2CW180A3)
  
• 3ware 9650SE RAID controller, Write Cache disabled.
  
• Ubuntu 12.04, ext3 file system. No system settings have been changed specifically for SSD.
  

What we get, for example for Sequential Read:

hdparm -tT /dev/sda<br>
<br>
/dev/sda:<br>
 Timing cached reads:   29078 MB in  2.00 seconds = 14555.91 MB/sec<br>
 Timing buffered disk reads: 592 MB in  3.01 seconds = 196.79 MB/sec

Seems to be satisfactory.

Sequential Write:

dd count=1024 bs=1M if=/dev/zero of=/opt/test.img conv=fdatasync,notrunc<br>
1024+0 records in<br>
1024+0 records out<br>
1073741824 bytes (1.1 GB) copied, 123.776 s, 8.7 MB/s

And here is the disappointment. I was expecting at least 100mb/sec.

What am I doing wrong? Or is SSD and RAID1 an inherently bad idea?

I can’t try just one SSD or Software RAID - this is a rented server.

Answer 1

We decided to enable write cache in the RAID hardware and SSD for sequential write showed 180MB / sec, in random write from 50MB / sec. It looks like you need a newer or more expensive hardware RAID than this one and it will work just fine.

Answer 2

So maybe to present a claim to the hoster - let him figure it out himself?

Answer 3

Yes, the results are quite sad, I recently drove the 4th vertex in the 10-ke .