SATA over SCSI

[Necrometal]

Getting together my wishlist for parts for a new server and Im curious if anyone has had exposure to SATA in a server enviroment yet.

Im still partial to SCSI, just want opinions and some realworld experiences.

[kannibul]

I would stick to SCSI, since it offloads the CPU from having to interact with the disks, and you cna get more bandwidth out of a SCSI bus, than with a SATA bus.

From a drive perspective, there is only one 10K SATA drive out there, while there are LOTS of 10K and 15K U320 SCSI drives out there. This equates to faster access times, and the faster a disk spins, the faster it can "sling" the data off.

I have two U320 Maxtor Atlas IV 36GB drives in RAID-0, with my LSI Logic MegaRAID Express 500 (64MB cache) - and I get 85MB/sec sustained transfer rates...

Remember, my LSI card is 32/33 PCI - so it's max theroritcal limit is 133MB/sec - in reality it would peak at 95-100MB/sec, but also remember that there are also other devices on the PCI bus and so on and on and on.

Anyhow, go SCSI if you can afford it. SATA if you can't.

[Platypus]

I'd think there's a long way to go yet before any firm conclusions can be drawn about SATA, and real world experience is likely to be thin on the ground. As mentioned by kannibul, Western Digital seems to be the only one yet putting forward an enterprise class drive with the Raptor.

Australian PC Magazine got some interesting results with this drive. It slaughtered the other available SATA drives not only on DTR, but significantly, on CPU utilisation.

For example in Single Drive High-End Disk Winmark, the Maxtor scored 24500KB/s with 58% CPU usage, the Raptor 33500KB/s at 10.5% utilisation. A Seagate Cheetah 10K.2 Ultra320 SCSI drive gave similar Winmark results, but at 90% CPU utilisation.

So it is possible that while SCSI retains the crown for high-end Multi-drive multi-threaded operation, SATA could give it a run for its money in less demanding single drive or RAID0 configurations.

[confus-ed]

Originally posted by kannibul
I would stick to SCSI, since it offloads the CPU from having to interact with the disks, and you cna get more bandwidth out of a SCSI bus, than with a SATA bus.

....Anyhow, go SCSI if you can afford it. SATA if you can't.

Oh humm ... this all depends on what motherboard you have it connected to !!!

I'll start by disagreeing with the first bit ... Never heard of DMA ?? - Scsi uses a system very similar (but with more potential overhead!!!) - now I'll disagree with the next bit !!...

The PCI bus has a maximum transfer speed equivalent to ata 133 ... so wether you connect SCSI or SATA this is as fast as you can go ... newer motherboards are designed differently & have a beast called ICH5 (interconnect hub) built into the chipset which lives between memory & the pci bus to enable fasster transfers (currently limited to ata 150) for SATA devices. You can't take advantage of this with SCSI as it connects to the pci bus.

But we said 'server' so maybes we have a 64 bit pci bus on our 'not known' motherboard then we can go as fast as we like (well we can go faster than any drive can supply)...

There's no actual difference in any of the disk technology we are merely talking about connection methods & buffering systems ... the disks inside the units are identical just spinning faster !

Since we don't 'know' what we'll be attaching this to or for what it might be used I'll go with the last line of the post above (which seems to be the only bit I DO agree with ! )

[Necrometal]

This was the board I was looking at, Intel also offers a integrated SCSI option for the same board.

It has PCI express so I guess it really doesnt matter which one I go with, since expansion later on isnt really a problem.

Like stated before, Im still leaning towards SCSI for the familiar enviroment if nothing else.

Although, if I could save on costs, still get nearly the same performance, and still be able to add on later on down the road. welll, I might just change my mind!

Ive been doing some reading and found some really serious hardware for SATA coming out within the next couple months or so. Increased bandwidth between drives and bus, some serious looking backplates for multiple redundancy, and a few of the other drive manufactuers are rolling out their 10k rpm line.

I hate it when your right on the fringe of adopting a technology when you need something soon. You dont wanna wait for business reasons, but waiting would get you something so much better.

[kato2274]

Originally posted by confus-ed
There's no actual difference in any of the disk technology we are merely talking about connection methods & buffering systems ... the disks inside the units are identical just spinning faster !

true but that does in fact make a difference (the rotational speed that is)

if I have two identical platters and one spins twice as fast (15K RPM vs 7200 RPM) which one is going to have faster seek times if for no other reason than simple physics.

for that reason alone (rotational speed) I'd be more likely to stick with SCSI on enterprise equipment that is until SATA can get drives approaching the 10K rotation speed.

[confus-ed]

Well you have a 64 bit bus ... so whatever you can afford !!

A mixture might be the answer ?? & give a lot of options ...

I find myself recommending SATA now where I would have said SCSI 160 will do it ... just on cost especially with 'larger' data storage requirements .... However when cost isn't an issue I still find myself using scsi - because I trust it !!

I still don't know what the 'typical' role of this server might be...

& edit for Kato ...

You can get sata drives that are 10k rpm ... & even 15k rpm !! Just like scsi !

[kato2274]

Originally posted by confus-ed


& edit for Kato ...

You can get sata drives that are 10k rpm ... & even 15k rpm !! Just like scsi !

really? I just went looking but couldn't find anything over 7200 . . . . . .must not be looking in the right places

[confus-ed]

Originally posted by kato2274
really? I just went looking but couldn't find anything over 7200 . . . . . .must not be looking in the right places

Just as an example ... Western Digital Raptor 36.7 GB 10,000 rpm & 5.2m/s seek ...

Admittedly 15k ones are harder to get (very very new)... the only ones I know are fujitsu ... is that enough said ?

[kato2274]

Originally posted by confus-ed
Just as an example ... Western Digital Raptor 36.7 GB 10,000 rpm & 5.2m/s seek ...

Admittedly 15k ones are harder to get (very very new)... the only ones I know are fujitsu ... is that enough said ?

I wasn't being a smarta$$ . . . . . . . . .if you got that impression. I believed you, I just didn't know that they had 10K SATA drives out there, but I tend to deal more with desktop / workstation hardware.

[confus-ed]

Originally posted by kato2274
I wasn't being a smarta$$ . . . . . . . . .if you got that impression. I believed you, I just didn't know that they had 10K SATA drives out there, but I tend to deal more with desktop / workstation hardware.

No offence taken .... I was 'surprised' when you said SATA drives were 7200 ... everyone I'd looked at/fitted were 10k ones... so until you 'pulled' me I hadn't even realised there was a 'cheapo' version

So let me make it clearer, when I say the only difference is 'connection' & price I'm talking about drives with simillar rotational speeds & thus seek time .... A touch of confus-ed-ness (which is to be expected with me around) that's all ...

[Necrometal]

Basically its going to be a box that holds our entire database. And run a front end for the client so they can access that database.

Speed is an issue, but since Im at a goverment entity...so is cost.

IM still teetering towards SCSI, like stated before. For its reliability and predictability.

[SpongeBob]

ok... flame me later... if this is repeated earlier...

SCSI is faster on a PCI64 bus.

any raid array on a standard pci bus or even it own pci bus is limited in bandwidth. (it sucks and your wasting money)


REAL servers (compaq, dell, IBM...) all use PCI64 or newer technology. they use u320 scsi.

The drives are faster, cheaper, more reliable. The application support for scsi is huge and maufacture support for product spec and defects are wonderful.

unless this is a test server, for home, or non-production level use, I would not try to build your own. BUY ONE! they are faster!!

Right now you cant really compete with price and speed of a "home built" server and a IBM/Dell/Compaq type of server.

For production level servers the custom bios with the array management in windows/linux is wonderfull with a manufactured server and you cant get that with a home made one. (unles you custom write your own bios!)

Sure you have some non-standard parts, this is why most enterprise networks go single vendor, and decide this in a pre planing stage.

[Six Eyed Smily]

in my opinion, the main thing that is holding sata back in the server market is lack of server class controller cards. for this reason, i personlly, would go with scsi for everything above entry level servers.

[confus-ed]

Originally posted by Six Eyed Smily
in my opinion, the main thing that is holding sata back in the server market is lack of server class controller cards. for this reason, i personlly, would go with scsi for everything above entry level servers.

Well yeah ... but give it a chance ! ... but this looks like an entry level server to me ... like I said where you might say scsi 160 say sata ? With the particular board he wants he can choose either ...