View Full Version : ata card normal versus raid

02-13-2003, 03:43 PM
here's an interesting question--

but let me paint the scene first, a dual g450 which i am turning into a server. I am putting in two ata pci cards so I can have a whopping total of 4 drives in the thing (!). I am basically reproducing what the xserve has-- an independant channel for each drive. Three of the drives will be large and will hold the files to be served to the other computers. The 4th will be system.

here's the question--
wouldn't it be better to simply use regular ata133 cards, and not raid all the drives to one volume? Since it is a fileserver, there will be multiple IO's. I am thinking that if 2 or three people are up or downloading large files, each copy will tax all the heads at the same time (though faster), but if I have 3 separate distinct volumes, there will be occasions where the IOs will not span more than 1 drive. Follow? So then the heads will do less work in those cases (though slower).

02-13-2003, 04:40 PM
Check out the database on www.StorageReview.com (http://www.StorageReview.com) and compare drives for file server benchmark I/O's and how well they perform. Due to the nature of SCSI's tagged command queuing which is incorporated into the IBM 180GXP, along with the larger 8MB cache, I don't think you'll be taxing your server in any event.

If you "short-stroke" your stripe volumes so you only use 50% of the volume, and partition it to only use the outer 2/3 of the drive anyway, you maximize density and outer track response (often 20MB/s faster than inner tracks) which will also reduce head latency. If you have four drives stripped, you effectively have the cache of each drive, 32MB in this case, holding data. Some controllers have 128MB of their own cache and ATTO FibreChannel cards go up to 512MB. Apple offers two FC cards, each dual channel.

You can put six drives in there (check out the drive upgrade section reports on www.xlr8yourmac.com (http://www.xlr8yourmac.com) ) and you might want five... you would end up with two RAIDs (HARD) which you could then stripe into one even larger volume... very unsecure but fast, using either SoftRAID or Apple RAID.

Two SIIG cards? I'd think your system would do fine enough on the native ATA bus. Just use the card for two of the best drives - and RAID that. Then have a couple backups - a single ATA 200GB internal, and another 200GB external FireWire maybe.

I'd start with a boot volume and two drives on SIIG or ACard HARD RAID. Try it with raid0 switch off, then try it on.

Rick's RAID database might offer clues.

Single drive: 45MB/s? HARD RAID: 90MB/s? Total cost: $600

Then there is SCSI http://macgurus.com/infopop/emoticons/icon_biggrin.gif

ATTO UL3D + 4 Cheetah 10K's ~200MB/s (for only $2500~ http://www.macgurus.com/ubb/rolleyes.gif

02-13-2003, 05:08 PM
partitioning the drives to only use the outer 2/3. interesting. can you refer me to more documentation on this voodoo?

can you explain what you mean with the hardware/software raid combo?

I think i understand you to mean: 2 hardware raids, and then merge them into a volume with softraid. Sounds hairy.
Or you mean, 2 drives per channel off one card. But I would get better throughput with ONE channel per card.

by the way, what is wrong with sonnet? I think they have better support. in fact, they have fixed the deep sleep issue with 10.2 with a driver.

acard and siig still are a little buggy with deepsleep, no?

[This message has been edited by jacob (edited 13 February 2003).]

02-13-2003, 05:50 PM
The voodoo is me from hanging out on StorageReview and learning to fine-tune my own (SCSI) RAID setups using SoftRAID and benchmarks. Think about it though. There's plenty of evidence to support it out there. You never want to fill a drive beyond 65% anyway, especially if it sees a lot of activity. Making your first raid volume for scratch the outer most is the fastest region. No voodoo.

The difference in price of SIIG cards is like $60. That is pennies. SIIG is just OEMing ACard and the deep sleep - or even plain olde sleep - issue was 'cured' in their last firmware which was in December. I use ACard myself (they make the card so they ought to know). They also added RAID1 to their firmware.

A good 144GB Cheetah 10K.6 or Atlas 10K IV delivers 60-77MB/s per drive. But at a cost of nearly $1000 each. Smaller drives are less of course. A good dual channel FibreChannel card from Apple for their XServe RAID is only $500. A dual channel ATTO UL3D is ~$600. Granite Cable + terminator $240 per channel. Which is why the UL4S is a good buy, you don't need as many channels, and its only $349.

Serial ATA (SATA or S-ATA) are SCSI-like only 30% cheaper, but SCSI in size (meaning 36GB, 73GB, etc.) but promise to begin offering cheaper controllers and cables? but able to deliver 160MB/s. I assume that is PER CHANNEL, rather than PER DRIVE. Otherwise, SCSI drives would likely perform the same or better, and 77MB/s is the best you can get today.

You've seen the prices on those XServe RAID 3U with all the goodies?

[This message has been edited by Gregory (edited 13 February 2003).]

02-13-2003, 06:24 PM
you sound as tired as I am.

I originally was going to do a 4d scsi raid, but the cost hit me in the head, and when I looked at the fact that i am serving over tcp/ip anyway, I decided ata will be just fine, and lots cheaper.
For local work, like doing billboard-sized composites on one of the retouching workstations, scsi would be ideal.

(Funny, computers are getting so fast, but there is only so fast people can work.)

02-16-2003, 02:02 PM
another thing I have been researching, and what I think was implied, is using the os x raid feature to raid two volumes, which are already raids of 2 drives.
so 4 drives on 2 different hardware ata raids (2 drives per card)
yields 2 volumes
then raid the tw volumes in os x.

is this crazy?

02-18-2003, 04:28 AM
Keep it up jacob -

That 733 QS I mentioned in your OS X Server survey is currently used for small data files, so non RAID ATA HDs are fine (with regular tape backup)... except we have a new group of users who are about to start saving all their large graphic/video files on it soon. I need to add space and also try to improve I/O performance, but still would prefer to have RAID 1 or 5 security....

So this is all very intersting.

While thinking about all this I went to Apple to read some more on the XRAID... thought I saw some where that multiple hosts were supported. Sure enough. Check this: http://www.apple.com/xserve/raid/deployment.html

This may very well be "it" for me. I have 2 mission critical servers that I lose sleep over because of lack of RAID 5, and several others that really should be RAIDed as well.

Not Cheap, but I have weigh the pros and cons of this vs. the aproach you guys are discussing on up to 5 servers... And one will need a 2 Gig FC card for each host; Apple's is 500 bucks. I wonder if 3rd party would be better/faster, sorta like Apple's history with OEM SCSI cards.

I guess the first step on the road to XRAID is to wait for some reviews and user feedback; can't afford to be bleeding edge with production boxes, right G? Then test, test, test! If it is not as awsome as it sounds, I may be buying ATA RAID cards too.

[This message has been edited by newbie (edited 18 February 2003).]