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Raid 0 3xSCSI super slow, need help

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February 12, 2008 3:51:44 AM

Hey Guys,

today I installed my first Raid array. Its a raid 0. I have 3 IBM 36GB 10k SCSI drives and Adaptec 2100S controller (32bit PCI).
Ive tried already stripe size 4kb, 128kb, and 256kb. No difference at this point. When I run a benchmark, eg. HD Tach it will give me nice average access time of 8ms which is expected, but then I get the burst speed of 60mb and average speed of 50mb. thats soo slow, even my ATA133 WD 160GB and WD 250 GB get better results in the range of 80mb for burst.

When I benched three drives seprately I got about 70mb burst and average of around 55mb. What is going on? I also have a picture of the HD tach results for the raid 0. I dont know how to upload it though. Its a straight line at around 60mb all the way.

Where is the problem?

I have WinXP. Athlon Mp2800+, 1GB ram. There is nothing on the raid0 saved so far, just empty, clean format.

Greg

More about : raid 3xscsi super slow

February 13, 2008 2:12:08 AM

Cmon 40 views and no response....

Is there any more info you need from me?
February 13, 2008 2:46:23 AM

RAID 0 has to bet setup with 2 or 4 drives.

You say you have 3 SCSI drives in a RAID 0 array currently...clear that up first.
Related resources
February 13, 2008 12:56:49 PM

Thats not true, raid 0 can work with 2 or more drives. raid 1 works with 2,4,6,8 drives.
February 13, 2008 1:31:22 PM

walukanis said:
...I have 3 IBM 36GB 10k SCSI drives and Adaptec 2100S controller (32bit PCI).
...but then I get the burst speed of 60mb and average speed of 50mb. thats soo slow...
...even my ATA133 WD 160GB and WD 250 GB get better results in the range of 80mb for burst...
...What is going on?...
...a picture of the HD tach...Its a straight line at around 60mb all the way...
...Where is the problem?...

I can tell you right away, it's pretty simple actually.

The max theoretical bandwidth of a PCI slot is
Quote:
Quoted from wikipedia:
peak transfer rate of 133 MB/s

But you also have to factor in overhead, encoding, etc., so it'll always be less. I think you usually average at about 66.6MB/s. I can't remember if PCI is a shared bus or not (meaning all PCI devices need to share the bandwidth), but that might be another problem. Do you have any other PCI cards? Some of your motherboard's connectors/IC's might be wired into the PCI bus. Either way, there isn't enough bandwidth on the PCI bus to support faster speeds.

That explains why you have a slow, yet constant sustained transfer rate (the picture of your HD Tach bench with a straight line). You drives are faster than your bus and/or controller.

If you want to get better throughput, get a PCI-e 2x or 4x (recommended) controller.
a b G Storage
February 13, 2008 1:33:27 PM

Check the termination of all three drives, and the host adapter(s). Is the SCSI cable too long?
February 13, 2008 1:35:00 PM

I have a 36gb 15k drive and a 10k 147gb drive on a 19160 controller.

I get about 63mbs average read and 36mbs average write on the 15k os drive.

I get 75mbs average read and 20mbs average write on the 10k drive.

Please note this isn't a raid setup.

I have an old 80gb 7200rpm 8mb ata100 drive that gets 55mbs read and 50mbs write.

I hate this as well. I found an article some place (wish I would have bookmarked it) that said XP has an issue with SCSI. Its something to do with some sort of file indexing in explorer.exe . So non explorer transfers work much better in XP.

I think its suppose to work better in Vista. I don't have Vista so I don't know for sure.

Don't feel too bad.

Also , you might want to google XP scsi bug.

Hope this helps
February 13, 2008 1:47:57 PM

After 20 hourse of hard research here is what I found out.
First off.
PCI is a shared bus with transfer 133mb max, and yes, there is overhead and what not but the transfers of 110-120mb/sec should be atteinable. I do have some other PCI cards, but its only USB hub with a mouse hooked up to it, so I dont think it takes a lot of bandwith.
I checked the cable, terminators, IRQ, switched to other PCI ports. No improvement.
WinXp does have a cache that makes it write slow to HDD if used with explorer, but there is an aftermarket patch that can be installed and that solves the problem. It wasnt my case though. I installed 2k3 as well just to try it out
My board doesnt have PCI e ports.
The problem is: The controller.
Adaptec 2100S is known for extremely slow transfers. Too bad I learned that after I bought the card. From other boards I leanered that actually 60mb/sec with this controller is an excellent score. Some people were getting as low as 20mb/sec.
There are other recommended controllers that can be picked up from ebay for cheap and that is what I did. I paid 20$ for the controllers (2 different ones + shipping) so its a good deal. I should be getting north of 100mb/sec.
Another step is actually looking for the new motherboard and CPU and RAM and PCIe controller :) 
Mylex AcceleRaid 170 or LSI MegaRaid Express 500 are the other cards that are worth recommending. All of them are PCI 32bit/33mhz.

Hope that helps for others. If you have any questions, just post and Ill try to answer what I learned

Greg
a b G Storage
February 13, 2008 2:02:53 PM

Nice job on the research.
February 13, 2008 2:04:43 PM

walukanis said:
Cmon 40 views and no response....

I tend to just grab the stuff that shows up in the crawler on the home page, sorry.

I see a couple of things going on here... First, HD Tach just doesn't measure RAID sets very reliably in my experience, so there's little certainty where the truth lay. Then there's the [32-bit] PCI bus, which is limited to that 133 mb/s max like gwolfman said, and yes, that bandwidth is shared with all other devices on the PCI bus, and just half-duplex too. PCI -based server motherboards often have multiple separate PCI buses (as well as support for non-standard PCI variations) as ways of working around this limitation.

And I'm not enormously surprised that you would see better burst rates from your ATA drives, especially since the IDE/ATA controllers tend to be closer to the bridging devices. For a better analysis you'd have to look at a logic diagram for your motherboard, and focus on how the PCI bus bridging is done.

ObReminder: Burst rate benchmarks are of limited relevance when it comes to actual production performance.

-B
February 13, 2008 2:09:22 PM

I found the site that has the info on the scsi/xp issue.

http://scsi.radified.com/

Scroll down to the section entitled "SCSI with Windows XP"

Looks like it could be the WRITE_THROUGH file flag issue.

btw: where did you get the patch ? I haven't tried that yet.

I also have my write cache turned on.
a b G Storage
February 13, 2008 2:11:29 PM

2x 7200rpm WD Enterprise disks, onboard Matrix RAID-0, 128k, 16mb cache, SATA 3GB/s, 105mb/s average read, 200mb/s burst :) 
February 13, 2008 2:13:07 PM

leo2kp said:
2x 7200rpm WD Enterprise disks, onboard Matrix RAID-0, 128k, 16mb cache, SATA 3GB/s, 105mb/s average read, 200mb/s burst :) 


You just had to rub it in didn't ya?

:fou: 
a b G Storage
February 13, 2008 2:17:28 PM

cah027 said:
You just had to rub it in didn't ya?

:fou: 



You know it haha. They're relatively inexpensive disks too. I should get a SS of my HD-TACH and HD-Tune scores. I know benchmarks don't show real-world performance but when you're beating raptor drives in the same benchmarks, it's hard not to feel proud :p 
February 13, 2008 2:25:38 PM

cah027 said:
I found the site that has the info on the scsi/xp issue.
http://scsi.radified.com/
Scroll down to the section entitled "SCSI with Windows XP"
Looks like it could be the WRITE_THROUGH file flag issue.

The caching issues aren't just Windows XP. Windows 2000, Server, etc. all make a somewhat silly assumption that if you spent the money on a RAID controller, that you would have spent money to buy one with it's own on-board caching.

But poor read burst benches are something else entirely.

Interesting about the OP finding lots of 2100S owners bitching. I went to Adaptec's web site to look for info about the card, just to satisfy curiosity since most of my Adaptec experience is with the 27xx, 39xxx, etc. but their site is borked right now...

-B
February 13, 2008 2:39:20 PM

pci express cards are definately the way to go
with my megaraid lsi controller pci e 4x i get burst reads of 320mb/s and average reads of 212mb/s
and i would of thought scsi would do better than 110-120 mb/s
February 13, 2008 2:52:10 PM

raptorxt said:
pci express cards are definately the way to go
with my megaraid lsi controller pci e 4x i get burst reads of 320mb/s and average reads of 212mb/s
and i would of thought scsi would do better than 110-120 mb/s



How many drive do you have in that array? Thats Crazy fast!
February 13, 2008 2:58:26 PM

cah027 said:
How many drives do you have in that array? Thats Crazy fast!

February 13, 2008 2:59:33 PM

Dang double post...!
February 13, 2008 3:40:06 PM

4 drives would be plenty for that result.... In Raid 0 ofcourse

Yeah go to http://forums.storagereview.net and search for 2100S, man...

I was reading and I couldnt believe myself.... That controller is terrible. Pretty much all of the Adaptec's U160 series controllers are crap according to them. U320 is a different story.... I wish my board would have PCI64bit/66mhz, like my old Server board used to.
February 13, 2008 3:56:31 PM

glad you figured it out. :) 
a c 117 G Storage
February 13, 2008 4:26:49 PM

The 2100 is a number I seem to recall seeing for years an years....and the drives seem a bit old too....my 1998 build behind me has 36Giggers tho they were replacements.....sometime around 2002-2003 IIRC. Areal density of drives has increased rapidly from the days when I built the box here so new drives are much faster than older ones. But I think the PCI slot and the old controller or the primary bottlenecks here.

February 13, 2008 4:36:31 PM

So do you guys think a u320 64bit pci-x card in a 32bit pci slot would give us better speed?

Also can you guys suggest a u320 card ? I am correct in thinking you can put a longer 64bit pci-x card in a 32bit slot, right?

I am seeing some on ebay for about $50 or $60

Here is one for $20 after shipping.

http://cgi.ebay.com/LSI-U320-LVD-2-Channel-MegaRAID-SCS...


**Edit**
I just read the op's reply earlier.Looks like I should look into Mylex AcceleRaid 170 and the other one he suggested....

Thanks
February 13, 2008 5:08:37 PM

Here is what I found out. The 66mhz 64bit cards should work as well, however they will work at only 33mhz (32bit) so the trnasfer will be limited to only 133mb/sec the same way as I am right now (U160). Drives are usually U320, cables are U320, so the card is the bottleneck.
If you can get a PCIe card, then its a different story, since the trasnfers attainable should be way higher.
As to card, the card you found (LSI-U320-LVD-2) is a great card, but dont get your hopes up. They go for north of 130$ if you search for them. The cards I posted (AcceleRaid170 and MegaRaid Express 500) are totally fine for the Desktops (U160). Put 2-3 in Raid0 and you are golden.

Damn there is one AcceleRaid 170 card on ebay I was going to bid on, but now I will be bidding against you :) 


Greg
February 13, 2008 5:10:52 PM

JackNaylorPE said:
The 2100 is a number I seem to recall seeing for years an years....and the drives seem a bit old too....my 1998 build behind me has 36Giggers tho they were replacements.....sometime around 2002-2003 IIRC. Areal density of drives has increased rapidly from the days when I built the box here so new drives are much faster than older ones. But I think the PCI slot and the old controller or the primary bottlenecks here.

The drives I bought were made in May 2003, which is 5 years. I know that they were around for quite some time, but their performance is still better than ATA. Random Access Time around 8ms, where ATA is around 12-14ms. Only Raptor has those times, and it is also space limited. I dont need a lot of space for system. 3x36 is about 100GB. who needs more than that for XP or 2k3 or even Vista and some software?

Greg
February 13, 2008 5:43:22 PM

walukanis said:
Here is what I found out. The 66mhz 64bit cards should work as well, however they will work at only 33mhz (32bit) so the trnasfer will be limited to only 133mb/sec the same way as I am right now (U160). Drives are usually U320, cables are U320, so the card is the bottleneck.
If you can get a PCIe card, then its a different story, since the trasnfers attainable should be way higher.
As to card, the card you found (LSI-U320-LVD-2) is a great card, but dont get your hopes up. They go for north of 130$ if you search for them. The cards I posted (AcceleRaid170 and MegaRaid Express 500) are totally fine for the Desktops (U160). Put 2-3 in Raid0 and you are golden.

Damn there is one AcceleRaid 170 card on ebay I was going to bid on, but now I will be bidding against you :) 


Greg



I was wondering if that was you that already had a bir on it. I think there was another one , I'll bid on that one instead. Ha ha..

Thanks

February 13, 2008 6:39:32 PM

singleturbovr4 :)  That would be me :) 
February 13, 2008 9:00:31 PM

walukanis said:
Hey Guys,

today I installed my first Raid array. Its a raid 0. I have 3 IBM 36GB 10k SCSI drives and Adaptec 2100S controller (32bit PCI).
Ive tried already stripe size 4kb, 128kb, and 256kb. No difference at this point. When I run a benchmark, eg. HD Tach it will give me nice average access time of 8ms which is expected, but then I get the burst speed of 60mb and average speed of 50mb. thats soo slow, even my ATA133 WD 160GB and WD 250 GB get better results in the range of 80mb for burst.

When I benched three drives seprately I got about 70mb burst and average of around 55mb. What is going on? I also have a picture of the HD tach results for the raid 0. I dont know how to upload it though. Its a straight line at around 60mb all the way.

Where is the problem?

I have WinXP. Athlon Mp2800+, 1GB ram. There is nothing on the raid0 saved so far, just empty, clean format.

Greg



I've got a 2100S with 2 147 gig 10k drives and I get an average of 36 MB per seconds. I'm considering a serial scsi setup (SAS) because you can still use SATA drives on them and the bandwith isn't shared. I just need to get a PCI-E mother that's x8. Anyone have any input on SAS?
February 14, 2008 3:06:19 AM

Get yourself a new controller instead of investing all that money into drives, mobo's and controllers. New controller will run you probably 100 at the most and you will get a performance that will be triple of what you have now.

Greg
February 14, 2008 1:35:29 PM

walukanis said:
singleturbovr4 :)  That would be me :) 



I see you . I took one for the team and bid on the other one that is more expensive. Thanks for the info dude.

February 16, 2008 2:47:22 AM

Yeah I lost mine. Some prick outbid me and Im super short on cash at this point... Oh well....

Greg
February 16, 2008 7:15:17 AM

I saw that. I am watching both.. I am cah029 .. on another auction
February 17, 2008 2:05:37 AM

I figured that. Im watching it:) 

Good luck with it.

Greg
February 18, 2008 4:16:52 PM

I won it. It probably wont come with Drivers , do you know where I can get them?

I will bench with my 19160 then with the new controller and post results.

!