[Solved] Does Sil3114 in RAID-5 mode realy suck this much?

[Joffer]

Hardware:
AMD64 X2 4200+
1GB RAM
Asus A8N-SLI Deluxe
WDC Raptor 74 housing Windows XP SP2
4xWDC250GB connected to the Sil3114 controller on mainboard.

In RAID-0 (all 4 drives) HD Tach 3 gives med a Sequential Read Speed between 90 and 120MB/s all over the "disk". Now, making it a RAID-5 system and doing a new test, it gives med 10MB/s max at the beginning and then it goes down to only 4MB/s. It can't be that bad?

 

[Bobthelost]

RAID 5 shouldn't be much slower than a single drive in worst case. Less than 50MB/s looks very wrong to me.

 

[Joffer]

Just as I post a problem I figure out/remember the solution! A RAID-5 array needs time to build. And firing up the 'task summary' for Silicon Image SATARAID5 GUI application just told me I was right:

3 Create RAID Group Raid Group 0 Active 10 16 % 9/11/06 11:25:54 PM 03:34:26

The last column is time remaining... very well.. I figured it out I think.. will do a new HD Tach 3 check tomorrow when I wake up.

Bobthelost - I would agree with you.. and hopefully I will get a much better result tomorrow when the RAID-5 is done building..

 

[Joffer]

Woooohaaaa It took almost 5 hours to build the raid-5. And now the speed test showed a result constantly between 90 and 105MB/s. I'm happy again!

 

[Peter]

Roundabout 100 MB/s is the maximum you'll ever get from a storage controller on legacy PCI (32-bit 33 MHz). You MUST now be happy, 'cause there's no more to come

 

[Madwand1]

RAID 5's typical problem, esp. at the lower end, is write speed.

 

[blckgrffn]

Can you configure for a hot spare with that controller?

Nat

 

[Steve]

Is Sil3114 a software or hardware RAID controller?

 

[Joffer]

Peter/Madwand1 - well.. I know, and it's more than enough.. I'm mostly going to store MP3, Pictures and Videos on this array. But yes, the writespeed is not that good. Unpacking a DVD ISO from rar files using 7-zip to my stand alone WDC250 disk (on nvidia controller) goes about 20MB/s, while doing the same to the RAID-5 "disk" is 6-10MB/s.. strange thing is that the CPU doesn't seem to work much at all.. mostly being between 4 and 5% while unpacking..

blckgrffn - yes you should be able to configure a hot spare, but you are only able to use 4 disks in total, so that leave you with the needed 3 and then a hotspare. Note that the system should be able to work with one disk removed, but with degraded performance and with the security as a raid-0 array, meaning no data security, so remember to replace a defunct disk fast. NOTE - Not testet yet, but will. Another software RAID-5 system running linux worked fine for weeks with a broken disk.. took me a while to notice the failed disk..

sm8000 - sadly, it's a SoftRaid controller. But then again.. it's not using that much CPU.

If it's interesting, here is the graph from HD Tach on my system (hw specs in first post):
Graph from HD Tach 3

 

[Peter]

When writing to a soft-RAID, the PCI bus is the main bottleneck ... with a three-drive RAID5, every write access generates traffic toward three drives. On such a slow bus, that means the CPU is mostly busy waiting for the I/O to complete, and won't even get to "doing" much actual computation work.

 

[Joffer]

True
And it looks like I've got another problem.. after a reboot the raid5 settings was lost somehow *confused*. Well well.. I'll figure this out too I guess.