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Discussion on Article:
Roundup: Seventeen SAS Hard Disk Drives

Started by: kokara4a | Date 10/26/09 06:40:26 AM
Comments: 5 | Last Comment:  10/28/09 06:08:59 PM

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1. 
Nice job folks. I have a 36GB Maxtor Atlas 15K2 SCSI drive - it's awesome. Good to see it's still holding up pretty well.

But related to the article - I've had these questions about SAS and I cannot find the answer anywhere. Is there some form of compatibility between SAS and SATA. Can a SAS drive be connected to a SATA controller? Can a SATA drive be connected to a SAS controller? I have some vague memory that at least one of those is possible but maybe I'm wrong. Maybe a link to your 2004 SAS article would have helped - I couldn't find it!

There's another storage-related issue that no one seems to have investigated. How does software RAID compare to hardware - both chipset and addon card implementation. I mean RAID 0 and 1 and maybe some combination, not RAID5 for instance. I wouldn't think there's any advantage to hardware RAID for such scenario. I'm mostly worried about NCQ with hardware RAID - does the controller make use of it? Does it expose it to the OS? I imagine an NCQ-enabled OS will automatically make use of it in the case of software RAID. But will a hardware controller, that hides the physical drives and exposes logical drives, know how to pass through or outright reimplement NCQ? For such a review, I would also test on Linux, cause that's what I'm using but I assume testing on Windows will highlight the same issues.

Thanks!
0 0 [Posted by: kokara4a  | Date: 10/26/09 06:40:27 AM]
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- collapse thread

 
Can a SAS drive be connected to a SATA controller?

Physically - yes, but will not work.

Can a SATA drive be connected to a SAS controller?

yes.

I'm mostly worried about NCQ with hardware RAID - does the controller make use of it?

yes.
don't worry be happy (c) Bobby McFerrin
0 0 [Posted by:  | Date: 10/26/09 08:03:15 AM]
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Thanks Bobby. But what I really worry about is the extra cost of those RAID cards. I'd rather have software RAID (which I also assume is more flexible in the way of configuration) and I simply want to know how much performance (if any) I will sacrifice.

Cheers
0 0 [Posted by: kokara4a  | Date: 10/27/09 05:25:20 AM]
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Sure software RAID might be more flexible, but it is proprietary to the operating system. Software RAID from on-board storage controllers and cheap storage controllers does not work for every OS. Also software RAID from the operating system like Windows 2003 Server does not work with GNU/Linux. If using software RAID from the OS and the OS fails to work, the possibility of losing your data is very, very high. Hardware RAID is independent with the OS. Hardware RAID can fail, but it will take a long time. The hard drives will fail before the hardware RAID controller fails, so your chances are slim that a hardware RAID controller will fail. The big difference between software RAID and hardware RAID is that hardware RAID provides you a status what hard drive has failed. Software RAID does not have a straight forward status which hard drive has failed. There are hardware port multipliers that could be a substitute for hardware RAID controllers, but only if your SATA controller supports port multiplier.

BTW, this question is best ask in xbitlabs forum or other forums.
0 0 [Posted by: jmurbank  | Date: 10/28/09 06:08:59 PM]
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2. 
Seventeen SAS Hard Disk Drives :::
I think (please do NOT shoot, just my personal opinion), that you can safely remove HDs with Less then 120GB capacity from this kind of tests...Well, unless they are EXcepTionally FasT.
Currently, It's really little sense.
0 0 [Posted by: VladimirOrlovsky  | Date: 10/27/09 10:25:09 AM]
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