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Going Deep Inside Xserve Apple Drive Modules
adamengst writes "If you've had an Xserve drive fail, you may have considered saving some money by putting a replacement drive inside its Apple Drive Module. That may be a false economy, though. TidBITS explains why, while pinning Apple down on exactly what goes into Apple Drive Modules and why they cost so much more than bare retail drives."
I was going to complain that this is not a very interesting story for 98% of Slashdot, who has never seen an XServe and is happier for it, but since the link is already slashdotted, I guess I should complain about that instead.
While I hate to copy it, the server being pummeled and reporting errors for 9/10 requests doesn't lead to ad revenue either, so here goes:
About a year ago, we bought an Intel-based Xserve with a pair of 80 GB SATA drives to act as our primary Web server. When the boot drive went flaky on us in October 2008, we were able to recover from the backup on the second drive and off-site backups, if a little shakily (see "TidBITS Outage Causes Editors Outrage", 2008-10-07). But although we were able to bring the machine back online, we didn't trust the drive that had failed. Since the Xserve has three drive bays, the obvious solution was to purchase another drive. Sounds simple, doesn't it? Not so much.
You cannot buy a bare hard drive and insert it into an Xserve, as you can with a Mac Pro (and having just added a drive to my new Mac Pro, I can say that Apple did a stunningly nice job in making it easy to add drives, especially in comparison to the awful approach they used in the Power Mac G5). Instead, Xserves require Apple Drive Modules, which are custom carriers containing drives.
For users accustomed to buying inexpensive hard drives, Apple's pricing on the Apple Drive Modules comes as a bit of a shock. An 80 GB SATA ADM costs $200 from Apple, and a 1 TB SATA ADM costs $450. In comparison, a bare 80 GB SATA drive can be purchased for a measly $35, and a 1 TB drive is only about $100. That would seem to point toward buying a new SATA drive and swapping it into the bad drive's ADM. However, when I started down that path, a number of problems arose, such that I bailed on a quick solution and simply purchased a new 80 GB SATA ADM to replace the bad one.
First, I wasn't sure whether my Xserve had SATA drives, as I thought, because System Profiler on the Xserve shows nothing on the SATA bus, instead including all drives on the SAS bus. (SAS stands for Serial Attached SCSI, and is a high-performance data transfer technology that supports fast SCSI drives and is downward compatible with SATA drives.) After some discussion with knowledgeable folks on the MacEnterprise list and careful reading of the drive details in the SAS section of System Profiler, it became clear that both SAS and SATA drives are shown in the SAS section, with SATA drives having "ATA" as the Manufacturer, and showing "Yes" in the SATA Device line.
Second, once I knew that I had SATA drives in my ADMs, I started investigating if there were any gotchas involved in replacing the drives. There turned out to be surprisingly little hard information about this, with some people having replaced an ADM's drive with no trouble and others experiencing performance or reliability issues. I did find a few discussions about how replacing drives isn't recommended, but giving no solid sources.
Confused, I contacted Apple to discuss why ADMs are so expensive in comparison to bare drives, exactly what an ADM does, what Apple recommends users do with failing ADMs, and whether or not replacing a drive in one is a good idea. That conversation revealed a great deal of interesting information about the ADM and shed some light on what people with flaky ADM drives should do.
Drive Selection -- The most important fact to know about ADMs is that Apple doesn't use just any drives. We've all benefited from the amazingly low cost of storage. But whenever manufacturers compete on price, they cut corners every way they can to reduce costs. Although drive reliability is generally good, everyone who buys bare drives regularly has a drive vendor they refuse to patronize due to bad experiences in the past. (As is often the case, these people all hate different vendors, depending on which one was having a bad run at any given time.)
Since the Xserve is designed to be in constant use - 24 hours a day, 7 days a week, for years at a time - Apple doesn't use the least expensive drives available, since those drives are designed for more normal duty cycles in desktop computers - 8 to 10 hours per day, with variable use during that time. Instead, Apple wor
The pixie dust is in the controller, not the platter.
Apple dude discovers that servers use, well, server class HDs and they cost more than normal ones.
Oh, and the 'sleds' that hold the HDs have some LEDs (cool!) and a controller board to work with the cooling system.
Like pretty much every other half decent server then.
I want a list of atrocities done in your name - Recoil
Sarcasm fail :(
Any life is made up of a single moment, the moment in which a man finds out, once and for all, who he is.
Wow, those Apple Disk Modules are cheap! A 1TB SATAII 7.2K RPM disk module for an EMC CX3 SAN runs about $1500. But I think they get to high grade the drive makers' inventory since they suggest only 1 hot spare per 30 disks.
The gist of the article is "We asked Apple why they're more expensive, and took their word for it." It's just regurgitated marketspeak about how Apple tweaks the firmware for the optimal performance, has special rubber on the grommets of the ADM that is specific to each drive to reduce vibrations, and how off-the-shelf drives are unreliable, slow, noisy, and hot.
They don't make an effort to verify this information at all. Because Xserves won't run with commodity drives, they can't do a proper comparison to determine how much is truth and how much is smoke-up-the-ass from Apple. This is such an astroturf article, it doesn't even pretend to be anything otherwise.
... nicely. Quoting TFA - "About a year ago, we bought an Intel-based Xserve with a pair of 80 GB SATA drives to act as our primary Web server. When the boot drive went flaky on us in October 2008, ... "
Welcome to pragmatism and reality - Drives fail all the times. So use cheaper drives in redundant mode, replace them with cheaper drives when they fail. You would have saved good amount of money even if the cheaper drives failed three time more than the costlier ones. (450$ for 1TB vs $100 for 1TB - from the same article.)
The summary makes it seems that there's no rhyme or reason why Apple charges more for their HDs and why can't the consumer simply replace it with a standard SATA HD. If you RTFA, it goes into a long list of reasons why. Whether you accept Apple's reasoning is another matter.
To begin, XServes use a HD module called ADM rather than simple HDs. On the new MacPros, they also use a module but those modules are designed to replace the HDs inside. For the XServe you apparently can't get a bare drive alone, you have to replace the whole module. The author begins to list the reasons:
And then the author concludes:
Well, there's spam egg sausage and spam, that's not got much spam in it.
Having worked in the disk mines of IBM many years ago, the SCSI disk controller is somewhat your pixie dust but the real reason is the disks, heads and other parts for the SCSI drives came from IBM's best manufacturing facilities. The deathstar ATA drive's parts came from the lesser manufacturing facilities. In theory a SCSI disk should not be much better than ATA but the reality is the best made, more reliable parts go to the high end more profitable products.
The special ingredient in XServe disk drives is... love. :-/
This retarded fluff piece aside, the reason people buy (and pay a premium) for oem "blessed" hard drive replacements is because they JUST FUCKING WORK. If I save $100 on a hard drive, but spend two hours dicking with the raid controller to get it to play nice, or find out that it is in fact 2 mb smaller then the other drives, and now the raid won't rebuild, or has some firmware issue that I now need to rig up something to update, etc. I've lost money.
There is value in having everything already tested, and all your equipment in a "supported" configuration. When you have problems it makes it that much easier.
The fact that this article was apparently written by someone who does not know the difference between SAS and SATA makes it completely worthless. Clearly they are not qualified to admin the server they do have, much less write articles about the technical benefits of apple drives over other replacements.
The people who write these articles are stupid and contribute stupidity to IT in general.
1) Apple calls these beefier models "server-class" drives; you may also see terms like "RAID edition"
There is simply no data to back this up. The vendors themselves do NOT do sufficient testing to make these claims ergo Apple can not make these claims. This parallels the so-called better failure rates of SCSI/FC 'enterprise' drives and consumer SATA drives. In the FAST paper by Schroeder we see the following quote.
". . . we observe little difference in replacement rates between SCSI, FC and SATA drives, . . . ."
2) Firmware - the closest thing to an argument here is "may prevent Server Monitor from being able to report on the drive's health"
3) Carrier - "Apple also told me that the rubber grommets that hold the drive to the ADM carrier are chosen specifically to match each drive's vibrational characteristics."
This leaves out the most important thing. "So what" - ok if the drives vibrational characteristics are not matched what happens. Is it significant? Where is the data to say so?
4) Extensive testing - Essentially arguing that Apple does burn-in testing (which you could easily do yourself) however...again from the FAST paper:
"Contrary to common and proposed models, hard drive replacement rates do not enter steady state after the first year of operation. Instead replacement rates seem to steadily increase over time."
Drives act like mechanical devices NOT electronic devices.
In general - have you EVER read an article with so many "may"'s and "possibly"'s? There's very little here that could be risk assessed (giving some kind of probability of some consequence) - which means it USELESS as advice. The parts that actually IMPLY some kind of probability/consequence are not well supported by the studies with the largest sample sizes.
Parts of this may be true (it's impossible to say, since they don't specify exactly what they're comparing) -- but even if parts are true, it's misleading at best. In fact, some of it doesn't even seem to make sense. Let's look at real price lists from Apple and dell.
First we note that Dell doesn't seem to offer a 73 GB drive at all, so it's not entirely clear what they're comparing. The most likely possibility appears to be Apple's smallest option, a 73 GB SAS ADM ($300) to Dell's smallest, a 146 GB SAS ($349). While it's certainly true that the prices are comparable, it's also true that the Dell drive is twice as big.
For 300 GB SAS drives, the Apple site shows $650 while the Dell site shows $699. While Apple's price is lower, it's certainly not even close to $200 lower. To get a $200 price difference, it looks like they compared the full price of a 300 GB drive for the Dell to upgrade price for the Apple (i.e. the price difference for changing from the stock drive to the 300 GB drive).
For 1 TB hard drives, they have something of a point, but not a very good one. Apple's price for a 1 TB SATA drive is $450, while Dell's is $639. They fail to note, however, that Dell also lists a 1 TB SAS drive (an option not available for the XServe) for $679. Taking this into account, it looks a great deal as if Dell is simply doing their best to encourage their higher-end customers to use enterprise-class SAS drives by offering them at a purely nominal incremental cost over SATA drives.
The original article attempts to portray the situation as Apple offering prices that are at least as good as, and often better than the competition. In reality, there appears to be only one reasonable configuration where the Apple is likely to be competitive: the one using 300 GB SAS. At the low end, the Dell offers twice as big of a drive as the Apple for a purely nominal price difference. For lots of storage, the Apple offers only SATA drives where Dell offers SAS. If you're storing 1 TB of data (or more) the incremental cost of SAS is usually fully justified. There are undoubtedly exceptions, but they're not particularly common.
The universe is a figment of its own imagination.
Yeah, but the kicker is, sometimes the support still sucks. E.g., we have (er, HAD; Apple pissed me off to the point that I literally have a stack of Xserves that can turn to dust for all I care) a bunch of Xserves and Xserve RAIDs that we used for various tasks, mostly Mac-related.
One day, the RAID Admin tool notifies me via email that I have a failing disk in an array. OK, no problem, call Apple. We're paying for support, you know.
The guy on the phone was friendly, and said the disk was on its way. The next morning, I have a package waiting for me when I get in. It's a drive module, yay! I go into the server room, yank the failed module (conveniently designated by a red light) and insert the new one. RAID Admin proceeds to tell me that there was an unexpected error. Huh? I try again. Same thing. No additional information, just "unexpected error".
I call Apple back, and explain the problem, they run me through some GUI diagnostics, and in the end, cannot solve the problem. I tell them to hold off on sending me another disk just yet.
After trawling the Apple forums, I find out, hey, I can get all of the diagnostics and logs from the CLI, too. They're way more verbose. Verdict: Apple sent me a disk of the wrong capacity-- the ones in my RAID are 74.5 GB and this one is 73.x or something. Of course, they're _supposed_ to know exactly what kind of disks I have; that's the whole point of the service. Anyway, it eventually gets sorted out, but after the RAID sat there, operating without a hot spare for about a week.
Now, if this were the end of it, I would be forgiving of Apple. But I've had other problems. We had a CD reader fail in an Xserve. The Apple on-site person came out for this one. When he left (without checking in with me, of course), it still DID NOT WORK. This is despite the fact that I set him up with a workbench, full complement of tools, power, keyboard, and monitor to test with. The problem? He never bothered to plug the new CD drive into the machine. This is shoddy service. MINIMALLY, you test the part you just replaced, right?
But the icing on the cake was when a controller module in our Xserve RAID failed. I call Apple and they overnight a part. When I open the box, I have... a CD-ROM drive? I call Apple and say, hey, you sent me the wrong part. The support guy went so far as to call me a liar on the phone. He said that such a mix up was "impossible". He was convinced that I was going to return the box with a CD-ROM drive in it, and keep the shiny new controller that they sent me. It wasn't until I faxed them photocopies of the accompanying paperwork that they would believe me that it was their error, and even then, they CHARGED me for a SECOND part! It took our A/P department about a month to sort that out.
So fuck you very much Apple. Fucking rot in hell.
(And yes, I typed this message on an iMac. I like punishment; what can I say?)