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SATA vs ATA?
An anonymous reader asks: "I have a client that needs a server with quite a bit of storage, reasonable level of reliability and redundancy and all for as cheap as possible. In other words they need a server with a RAID array using a number or large hard drives. Since SCSI is still more expensive than ATA (or SATA), I'm looking to using either an ATA or a SATA RAID controller from Promise Technologies. While I had initially was planning on using SATA drives, I have read some material recently to make me rethink that decision and stick with ATA drives.
What kind of experiences (good and bad) have people had with SATA drives as compared to ATA drives, especially in a server type environment?"
3ware is another (some say superior) hardware RAID controller.
One thing about SATA is that it's easy to remotely mount the drives. You can easily put them outside the machine (in a rack or whatever) for enhanced cooling. They're kinda like really fast firewire drives.
The ratio of people to cake is too big
I bought a machine from with a controller from Promise and I think I know how they got the name. They kept promising me things.
I was using SuSE 8.2 and they had no drivers but they "promised" that they would be out by the end of the month. Of course I could compile them myself but since that required installing the OS which was impossible without the drivers that required finding another machine and dealing with other problems.
After about 3 months of "promise" after "promise" (this month for sure) they told me it the drivers would be out "in a couple months". The longer I waited the longer away the drivers were scheduled.
It wasn't like I had grabbed 8.2 when it was released either. Promise's Linux "support" was way behind and they basically told me that Linux is their poor stepchild that gets leftover resources when Windows stuff is done.
I contacted my vendor and had them swap the Promise card for a 3-ware. I tossed in the disk and loaded SuSE without any need for downloading or compiling drivers. I'm running RAID-5 on 4 120GB drives. I had a drive fail a couple months back but just hot-swapped/rebuilt it with no problem. The machine was up for about a year before I had to shut it down to replace a failed tape drive but I've had no trouble with the 3-ware.
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"You are not remembered for doing what is expected of you." - Atul Chitnis
Their IDE RAID card, the SuperTrak SX6000 does REALLY poorly at some tasks. It eats CPU and from mailing lists has a lot of problems recovering from drive failures. For a good comparison to other ATA RAID cards see this storage review writeup on it.
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SCSI drives tend to have the same size (or larger) caches as [S]ATA drives. You can disable the write-behind caching on any drive fairly easily using hdparm. ( hdparm -W 0 /dev/... to disable, -W 1 to enable).
Of course, if you are using a hardware RAID controller, you'll have to figure out how to tell it to disable the write-behind cache on the drives under its control. Perhaps it will be smart enough to figure it out if you use the hdparm command on the logical device it presents to the operating system, but I'd certainly want to read the manual and find out.
I know from experience that Windows 2000 automatically disables write-behind caching on drives in software RAID arrays (and dumps some Informational messages in the system log to let you know what's going on).
Every cloud has a silver lining (except for the mushroom shaped ones, which have a lining of Iridium & Strontium 90)
You may be right about building a system as reliable, and it'd certainly be hard to compete with it from a size standpoint, you are totally wrong about it being inexpensive.
Apple's 3.5TB system costs $10,999 US. If you were to build a system that comprised 9 Hitachi 7200RPM 400GB drives, you would acheive 100GB more storage space for 3,600$ plus the cost of the server it was hosted in. Throw in 750$ for a high-end RAID card and 1000$ for a server to enclose and handle it, and you're still priced at under HALF the price of Apple's solution.
So, in conclusion, Apple's solution is many things, and is certainly VERY sexy and attractive. But inexpensive compared to a self-built solution it is NOT.