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?"

Comments

Don't use Promise, for one thing

[b00m3rang]

Promise and Highpoint (and any other cheap raid card) in my experience are no more than an IDE card with RAID software that eats up CPU cycles. Recovery options for a lost drive member are usually limited and unreliable. If you want reasonable reliability, go with one of the drives that uses SCSI hardware adapted to an SATA interface (such as WD Raptor). I would personally recommend Adaptec for your host controller needs, as they do the RAID in hardware.

Re:Don't use Promise, for one thing

[Cthefuture]

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.

Re:Don't use Promise, for one thing

[UserChrisCanter4]

Don't confuse the fact that Promise produces on-mobo RAID "hardware" with the impression that all of their equipment is like that. Promise makes several truly hardware-based SATA and ATA cards, as well as a few enclosures that take numerous (4-16) IDE drives, do RAID in hardware, and interface to a server over U160 SCSI. They are perfectly capable of making hardware RAID solutions, provided you're willing to buy something other than a $60 "RAID" card.

Their only major drawback I saw last time I looked at their hardware was that Linux drivers at the time tended to be binary and proprietary to specific versions (works on redhat but not Suse, etc.), which may or may not matter depending upon the OS you're choosing to run.

I don't work for them, and I don't even use their equipment in any of my stuff (a buddy of mine runs an SX4000 card, though, so I have seen them in action), but I do get a bit peeved when someone dismisses a company's higher-end solutions because of (admittedly) bad experience with their low-end kit.

Re:Don't use Promise, for one thing

[afidel]

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.

no-brainer

[gyratedotorg]

if you're looking for reliability, this seems like a no-brainer to me. sata all the way. im not aware of an ata drive that even comes close to the 5 year warranty of wd's sata drives.

It's all in the name

[linuxwrangler]

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.

Dangers of using ATA or SATA for Raid

[DocSponge]

You may want to read this whitepaper and see what they have to say about using ata or sata drives in a raid configuration. It is possible, due to the use of write-back caching, to lose the integrity of the raid array and lose your data eliminating any intial cost benefits. To quote the paper:

Though performance enhancement is helpful, the use use of write back caching in ATA RAID implementations presents at least two severe reliability drawbacks. The first involves the integrity of the data in the write back cache during a power failure event. When power is suddenly lost in the drive bays, the data located in the cache memories of the drives is also lost. In fact, in addition to data loss, the drive may also have reordered any pending writes in its write back cache. Because this data has been already committed as a write from the standpoint of the application, this may make it impossible for the application to perform consisten crash recovery. When this type of corruption occurs, it not only causes data loss to specific applications at specific places on the drive but can frequently corrupt filesystems and effectively cause the loss of all data on the "damaged" disk.

Trying to remedy this by turning off write-back caching severly impacts the performance of the drives and some vendors do not certify the recovery of drives that deactivate write-back caching so this may increase failure rates.

Losing data on an ata raid array happened to a friend of mine and I wouldn't advise using something other than SCSI without understanding the ramifications.

Best regards,

Doc

I made a new years resolution to give up sigs...so far so good!

Re:Dangers of using ATA or SATA for Raid

[FueledByRamen]

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).

Re:Dangers of using ATA or SATA for Raid

[Guspaz]

This would be why professional ATA RAID solutions have battery backup. Somebody previously linked to Apple's XServe solution. It has enough battery backup power built in to keep the caches going for 24 hours. If you can't find a power source for your server within 24 hours of a power failure, your data obviously isn't that important.

First off I'd assume if your data is so important you're going to have UPS and generators. If you don't have a generator, and the power fails, great, you've got 24 hours to purchase one. A 1500W generator costs about 450$ US, and should be more than powerfull enough to run your server, AND network connectivity. You'll not only keep your server happy during a power failure, you'll be able to keep using the server.

Anyhow, this post started out about the battery backup. What you stated as a major problem isn't one, since serious ATA RAID solutions have battery backup.

Client/Server

[soundsop]

I have a client that needs a server.

On a related note, I was having dinner at a restaurant and my waiter asked me for a recommendation for a good email program. So I guess it turns outs that I have a server that needs a client.

Re:Buy a RAID

[Guspaz]

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.

Don't Confuse

[Crypt0pimP]

The connection technology with the drive / spindle quality.

(P)ATA and SATA are connection technologies.
They have their individual benefits and drawbacks
(cost, reliability, speed)

The real factors to consider are the details of the drives themselves - vibration dampening, bearing and motor quality, MTBF.

It used to be rather simple to guess what quality of drive you were buying. If it was 146GB or less (73GB, 36GB), and rotational speed was 10K or 15K, it was either SCSI or FC, and an "enterprise" class drive, rated in Mean Time Between Failure.

Good drive, high quality, expect it to last several years, spinning 24 hours a day, sustaining high read and write activity during production and backup hours.

If the drive was larger (200GB+) and slower (7200 RPM), typically an ATA drive, maybe low end SCSI.

Then it was, at best, a workstation class drive, rated in "Contact Start Stops", meaning how many spin-ups and shutdowns the drive should survive. Not meant to run 24 hours a day, and run under heavy load except for short periods.

The lines are beginning to blur with 300 - 500 GB drives with FC drive attachment. Those drives are meant for archiving and reference data. Not production databases and such.

In my personal experience, the 3Ware products are worth the premium.

Pick your attachment technology as appropriate.

Best of Luck,
Patrick (slineyp at hotmail dot com)

Experience...

[poofmeisterp]

The backplanes on server cases are horrid for SATA. They work, but you have to have special hookups for the LEDs (drive fail and activity) and often the controller cards or motherboards don't supply them. All I've managed to get is power LEDs on the front of the Super Micro cases I've worked with.

SATA is not that much faster in practice than PATA, because the kinds of load that you put a drive under in a production environment are not like the speed/load tests used to generate benchmark numbers.

You asked for opinions, and mine is that PATA (ATA-133) is more than fast enough, and the cost of SATA and the quirks that have yet to be ironed out are not worth it. It's the latest shiny object, and shiny objects are not always the most useful.

I base my experience on the Western Digital SATA (mostly 36 gig) drives and the Western Digital 40 and 80 gig JB drives connected to multiple brands of motherboards and add-on controller cards.