Apple Mojo In High-End Storage

by Robin Harris on Tuesday, 27 June, 2006

As an aside noted yesterday (see “Bring Me The Head Of WinFS“) that with the demise of WinFS in Vista, Apple has an even greater opportunity to stick it to Redmond by incorporating the leading edge open source ZFS file system cum storage manager into the next major release (Leopard) of Mac OS X (for more on ZFS see ZFS: Threat or Menace?.

Quality Low-Cost Storage For the Rest of Us
Apple’s rumored adoption of ZFS would also add significant Mojo to its server and its Fibre Channel Xserve RAID storage business. Xserve RAID has Apple’s typical design goodness and management simplicity, combined with industry-leading pricing of less than $2k per Terabyte. To do that the Xserve RAID’s RAID controllers dropped the expensive and tricky dual ported cache that enables controller failover. Unless you use server-based RAID, the loss of a controller means the loss of access to the disks behind that controller, so Xserve RAID isn’t enterprise class.With ZFS they’d have high-performance dual-parity RAID in software that would make a virtue of the Xserve’s RAID architecture.

This would be too smart for words. Steve Jobs’ modest investment in Xserve RAID and Xsan shows he is willing to push the envelope on Apple’s high-end storage as long as it doesn’t cost anything. ZFS support in Leopard would fit the bill perfectly.

Oh, And One More Thing
Expect Apple to announce soon a 10.5 Terabyte Xserve RAID configuration for $15k, dropping it to under $1500/TB. This translates to 147 TB in a 42U rack – over 12 TB per square foot. Will it go to 4Gb Fibre Channel and SATA drives? Stay tuned.

Update 2.0
For more on what ZFS on Leopard would mean see this post.

Update 1.0
Alert reader ZDigital pointed out that Xserve RAID does have dual-redundant RAID controllers, so I modified the post.

The original post:

To do that Apple dropped dual-redundant controllers in favor of server-based RAID, so Xserve RAID isn’t enterprise class.

The correction:

To do that the Xserve RAID’s RAID controllers dropped the expensive and tricky dual ported cache that enables controller failover. Unless you use server-based RAID, the loss of a controller means the loss of access to the disks behind that controller, so Xserve RAID isn’t enterprise class.

Comments Welcome

{ 17 comments… read them below or add one }

hmurchison June 27, 2006 at 10:12 am

I’d love to see what Apple could do with ZFS. A lot is over my head but the storage stuff gets my mojo going.

I’d also love to see Apple update the Xserve RAID with SAS/SATA support and 4Gb Fibre.

They could also impress me with a 1U Xserve RAID with 10 SFF drives.

ZDigital June 27, 2006 at 2:07 pm

I believe you have an error in your article. You incorrectly state that the Xserve RAID “dropped dual redundant controllers in favor of server-based RAID, so Xserve RAID is not enterprise class.” Obviously this is incorrect, if you go to the Apple pages on the Xserve RAID you will see that dual redundant controllers is prominent mentioned and featured. It is true that the Xserve uses software RAID (if you don’t buy the optional RAID controller, +$500.00) but the Xserve RAID itself is very much enterprise class. I won’t argue that including ZFS would be great and give Apple another checkmark. It is important that we pay attention to the imminent storage hardware coming from Sun also.

Robin Harris June 27, 2006 at 3:21 pm

ZDig: You are correct: Xserve RAID does have dual redundant controllers. However, the controllers do not have a shared cache, so in the event of a failed controller, the disks behind that controller are invisible and access to the data is lost. That is why Xserve RAID is not enterprise class.

Thanks for catching that. I’ll correct it.

ZDigital June 27, 2006 at 10:04 pm

Thanks for clearing that up and upon further reading of the Apple’s Xserve RAID info, it would seems that they are actually playing up the fact that the RAID controller are independent. What they are saying in effect is that you have two RAID arrays housed in a single physical container as opposed to a single logical volume with dual controllers for redundancy. The next logical step would be for Apple to start shipping the RAIDs with the new larger 750GB hard drives in PATA to eek out a bit more life from the current hardware before turning to SerialATA and faster FC connections. Whether this is being sensitive to enterprise needs for a stable hardware path or maxing out profit from the initial investment, only Apple knows.

Keith L. Dick June 27, 2006 at 11:07 pm

All I can say is: Go Apple!!!!…

Redmond maybe will learn one of these days that it’s losing it’s leadership and there are now coming along other alternatives that may be more promising to the computing world…

Yeah I still use Windows but I hope in the near future that can change…

Storage Dude June 28, 2006 at 3:06 am

Where does this rumor come from? Why would Apple
spend so much time porting a Solaris file system into
FreeBSD? (not easy by a long shot) How would ZFS work
with the existing hardware RAID products out there?
(ZFS is designed to manage individual disks itself, unlike
most file systems) This one seems fishy to this Storage Dude.

Jim June 28, 2006 at 4:15 am

“enterprise class”…not quite. I manage 10 Xserves and 15 XRAIDs in an enterprise. They are not enterprise class hardware. The XRaid admin tool is laughable to say the least. buggy, slow, temperamental. And the XRAID is simply two independent RAID devices shoved into one form factor. Why you just can’t build one raid 5 volume with both channels is beyond me.

Robin Harris June 28, 2006 at 7:55 am

Jim, agree that Xserve RAIDs aren’t ready for prime time. With ZFS Apple could simply go to JBODs – lose the controllers – and be way ahead of where they are now. And ahead of Vista as well. See today’s post, when I get it up.

Storage Dude, actually much easier to port ZFS than to build a new file system. And all the RAID hardware goes away – you don’t need it. ZFS does “manage” individual disks by simply adding them to the storage pool – which is a Very Good Thing. More on today’s post.

ZDigital, the smart thing would be to lose the controllers entirely – why spend the money? You might leave the battery backed-up write cache for folks who want every bit of small write performance they can get, but even that would be a small advantage IMHO.

Don Smith June 28, 2006 at 9:30 am

Good move for Apple. We’ve seen a slow, methodical move towards gaining market share. 1st getting non-computer consumer product domination with iPod. Followed by gaining back mindshare with consumers with iMacs, Macbooks and Macbook Pros. We are starting to see a bigger push with creative pros (Final Cut, Aperture, Logic Pro, Shake, etc.). In these markets no other company offers such a range of HW & SW. No one comes close.

Now if they could just get some business to take a look at them. Maybe this is the “killer app” for business (albiet, not an app) to go along with Mac OS X Server products (HW/SW) and they could have a minor hit…. now if they can only get Pixar to use this stuff 🙂

Wes Felter June 28, 2006 at 7:13 pm

I agree with Robin Harris; let’s lose the RAID and replace it with SAS/SATA JBODs at $1K/TB.

web design uk June 29, 2006 at 6:32 am

Where can I get me some !!

Gary Watson June 29, 2006 at 9:39 am

Xserve RAID does NOT have redundant RAID controllers. You have two 7-drive RAID controllers in the same chassis. The definition of redundant RAID controllers is that in the event of a controller failure, the survivor can take ownership of all drives and present their data to the host. In the Xserve RAID, each controller is only connected to 7 of the drives, so if a controller fails, you lose access to the other 7 drives. Period. It’s true you can make two 7 drive RAID sets and then mirror them, but now you have only 6 drive’s worth of effective capacity with no hot spares even though you paid for 14 drives and a big chassis. Kinda trashes the low cost/GB argument especially if you need No Single Point of Failure. Even if you don’t care about this, you still need at least two parity drives and then you don’t have a hot spare. If you want a hot spare, you need one for each controller, so now you have 10 drives worth of capacity. Apple could easily OEM any of several fully-featured RAID controllers from Infortrend, Nexsan, or LSI and solve this problem in a few months and get a huge performance boost.

Robin Harris June 29, 2006 at 11:49 am

Didn’t I say they weren’t redundant? Lack of global hot spare means each group of seven needs one unless you like living a little closer to the edge. Frankiy, if your data is mission critical you probably aren’t using Xserver RAID anyway.

The performance boost from RAID controllers is largely due to the NVRAM write cache, which is already an option on Xserve RAID. So going through the pain of an OEM qualification, which the miserly funding of the Apple storage team wouldn’t allow anyway, wouldn’t buy them much in performance. It could improve their availability. But not as much ZFS.

Robin Harris June 29, 2006 at 11:52 am

Oops, now I see what Gary Watson was referring to. Start brain before putting mouth in gear. He is correct that the alert reader mis-identified the Xserve RAID controllers as dual redundant. The best I can say is that there are two of them and with ZFS they’d be truly redundant.

rocksandwater August 23, 2006 at 1:22 pm

Apple will move to SATA/SAS when PATA drives no longer have a cost advantage.

XServe RAID might not be “enterprise class”, but for many applications, the price/performance is compelling. I’ll let Enterprises pay 2x-3x, while I meet my needs. I’ve got 8 XServe RAIDs and wish I had more.

Now, if I could just figure out how to backup a Mac Mini with ten 750 GB Firewire drives attached (under $1K/TB))…

Add ZFS and I’d be a very happy camper.


Vladimir Ivanov December 18, 2006 at 11:55 pm

I don’t think, zfs will make the system any better. First, if you loose one controller or a cable, you will loos access to 7 disks (there is no path redundancy). If you want keep access to your data, you should build a software RAID on top of the xRAID – but that was possible before zfs – MacOS had software RAID1 implementation at least in 10.2.

So, zfs doesn’t bring anything for xRAID, sorry. And the device itself is nothing special, seems to be an OEM version of some 2nd tier storage vendor array.

Robin Harris December 19, 2006 at 6:59 am


Certainly, for important data you’d want to mirror across both sides of an Xserve RAID. If you don’t, then there are several SPOFs.

Yet I disagree with you on one point: ZFS DOES bring significant value to low-end hardware – which Xserve RAID is – by enabling pooling, improving data integrity and implementing a solid RAID model, among other things.


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