How to speed optimize SATA RAID5 implemented with Lycom/JMicron card

axisofevil · 12-06-2012, 11:58 AM

I'm using a Lycom ST-158 card ( JMicron chip, here http://www.lycom.com.tw/ST158.htm ) to implement a RAID5 on an embedded system. The card is attached directly to SATA controller on SoC. Libata in kernel 2.6.

What can I do to optimize speed - especially read?

1) It appears to properly be doing SATA II ( 3 Gb )

2) I made ext3 fs with 8-sector alignment

3) read-lookahead didnt seem to help much

4) hdparm reports logical & phys sector size of 512 though the WD disks are 4096. I guess the card isnt transparent for 4096?

5) hdparm reports udma6

Pearlseattle · 12-07-2012, 02:57 PM

Hi
Well, perhaps it's already achieving its max speed when reading?
Did you perform a simple benchmark (e.g.

Code:

time dd if=myfile of=/dev/zero

) to see how fast it is right now?
Cheers

axisofevil · 12-07-2012, 05:30 PM

Yes - on 1GB files R/W from RAID( read from /dev/zero or written to /dev/null ) - I'm getting usually about 107MB/s read, 72 write. Its maybe 10% higher going straight to one of those disks without the RAID card ( which is in RAID5 mode using 3 disks ). But it does seem to vary across runs quite a bit.

cascade9 · 12-09-2012, 05:48 AM

That looks to be a port multiplier rather than a 'card'.

If you have 4K sector WD drives that report as 512b, you'll want to make sure you get the partitions aligned.

Pearlseattle · 12-14-2012, 12:33 PM

Do you think that your embedeed system (bus) + Lycom ST-158 card would be able to provide more than those 107MB/s read?

axisofevil · 12-17-2012, 10:21 AM

Yes it did with an SSD - around 250.

Pearlseattle · 12-17-2012, 04:41 PM

Bah - if you get 250MB/s with an SSD and ~120MB/s when using 1 HDD, I would expect you to get ~200 when using the raid5

When you read from the raid5 and have a look with "htop" and/or "nmon" at the CPU usage, does it go up a lot?
Btw., you're using the Linux software-RAID, right?

axisofevil · 12-18-2012, 10:24 AM

Sorry - the system without the lycom card , just SSD, did ~250;

the system with 'normal' drive ~120

Whenever I did raid I used the CARD to to rAID , not linux SW raid. The system is ignorant of any RAID capability - it just sees the 3 drives as one, with size = 2x of one drive.

System isnt up right now but I'll check CPU etc, but I doubt anything unusual since there's no system knowledge of RAID.

I'm thinking its as good as it gets.

Pearlseattle · 12-18-2012, 02:38 PM

Do you want to try perhaps to benchmark the SSD when connected to the card (in a non-raid configuration of course) to exclude that the card itself slows down the transfer?

Still have a look at the CPU, you never know - perhaps your HW-card implements RAID5 in software in the drives of the card itself => if the driver is not as good as the usual/normal SW-raid of the Linux kernel that might have an impact... (lazy - I did not check your card in the Internet).