SATA vs ATA? 111
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?"
Re:Don't use Promise, for one thing (Score:4, Informative)
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.
It's all in the name (Score:4, Informative)
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.
Re:Don't use Promise... (Score:3, Informative)
These things look pretty (Score:3, Informative)
StoreCase Technologies [storcase.com]
RAID boxen with ATA on the inside, SCSI and/or FC on the outside. Seemingly incredable warrenties of as long as 7 years.
Re:Don't use Promise, for one thing (Score:5, Informative)
Re:Dangers of using ATA or SATA for Raid (Score:4, Informative)
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).
Re:Buy a RAID (Score:5, Informative)
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.
Re:Buy a RAID (Score:2, Informative)
3ware + ATA hotswap trays (Score:2, Informative)
If you're going for more than just 2 or 3 drives and want to go SATA you should go with one of the newer multilane connectors. One connector carries 4 SATA channels and for an array with 12 drives you only have to worry about 3 cables. That makes the cable layout much neater and the connectors are fairly solid.
Re:Don't use Promise... (Score:3, Informative)
I haven't experienced any issues like that, and can confirm that the hot-swap and hot-spare capabilities work as expected on the 9500-12. I have not performed any benchmarks on the system, but have not experienced any read/write delays, which is probably helped by the cache of the controller and drives. I have 12 250GB drives, a mirrored pair for the OS, and a 9 drive level 5 array, with one hot spare. Pull any drive, and the hot spare works correctly, and the missing drive is rebuilt when plugged back in. Works exactly like the Adaptec 7902/2010ZCR solution in our SCSI servers, except the drives are about half the speed.
The few complaints I've seen about the 3ware cards are very similar to what you've said, though, but seem to be limited to a few specific OS/software combinations, which leads me to believe that: a) Few people realize what impact specific RAID levels have on performance (e.g. RAID 5 requires reads from all disks during a write to calculate the parity information.), and how certain hardware may reduce that impact (or in the case of PATA, significantly increase the impact of that specific problem), and b) There is some sort of issue with a specific type of read being performed by NFS, either a filesystem driver problem, or a hardware driver problem, possibly both.
As a quick summary, the major problem with PATA cards is that they use the PATA interface, command set, and drives. For speed, each drive should have it's own channel. The benchmarks you gave suggest other problems as well, and the older (PCI/33) controllers may have bottlenecks at the bus, but the newer cards (PCI-X/133) eliminate that issue for PATA/SATA drives (since you shouldn't use either if speed is your primary concern). If you want CHEAP, LARGE, and RELIABLE storage, the 9500 works well. If you want FAST and RELIABLE, a dual-channel U320 Adaptec RAID card works wonders, and it's nice to hit 640MB/sec instantaneous transfer speeds, with actual continuous reads at almost 600MB/sec, and writes at about 280MB/sec (RAID 1+0, 6 15Krpm drives, mirrored across channels, striped within channels).