Hi, I know Lion isn't out yet, but does anyone already know if a software RAID 0 (2x1TB) created using Disk Utility in Snow Leopard will be recognized by a clean install of Lion? (Let's assume you can do a clean install of Lion)
If not, will a software RAID 0 created in Lion be recognized if I boot Snow Leopard from a second drive?
The reason I ask, is that this RAID 0 has files on it that I'd like to be able use in both operating systems.
Mac Pro, Mac OS X (10.6.8)
In the past, sometimes an array created with the new OS was needed if you want to install on the array. Also, the array in Tiger could not be mounted by Panther 10.3.x
Some of the same for 10.5 and 10.6,
If they are just data, should be fine, but I would still have a couple backups and rebuild the array totally with Lion. Though I would also wait beyond testing for 10.7.2 also. I've never seen Mac OS X come out of the gate ready for prime time.
Thanks for the reply!
For clarification:
The RAID contains only data (two other disks would each have an OS installed on them).
You're saying a Lion-created RAID for data *should* be fully supported by Snow Leopard, even though it is created using a (supposedly) newer version of Disk Utility?
Seeing the trouble with previous versions, I would assume that Apple only supports RAIDs created an used by one version of OS X.
Though, I will definitely heed your advice about waiting until Lion has been properly tested in the "real world."
The Hatter's warning was about a problem with BACKWARD compatibility. The older RAIDs were forward compatible, but not optimum until they were backed up, re-created, and restored.
RAID-ness is a property of the Drives. It is not just a bit flipped in the Mac OS. You could remove those drives, install them in a completely different Mac, and they would still be a RAID.
Now whether that will be completely BUG FREE in the new OS remains to be seen. Want to be on the "bleeding edge" ?? Willing to risk losing your Data ??
Well, no, I wouldn't want to risk losing my data more than I'd have to. Which is why I have another question. đ
You say: "RAID-ness is a property of the Drives. It is not just a bit flipped in the Mac OS.".
If that is so, why would you need to recreate a software RAID under the new OS to make it 'optimum'? That implies that the two OS'es treat RAIDs differently. Which in turn seems to imply that using one software RAID under two OS'es intermittently is a bad idea.
Also, yes, The Hatter was talking about backward compatibility, but that is what I was wondering about: should a Lion-created RAID for data (whether or not it is bug free) be fully supported by Snow Leopard? Following your reply, and The Hatter's reply, that indeed seems not to be the case.
I'm not doubting your wisdom, I just want to make sure I understand what you mean. đ
I could just recreate the RAID under Lion and use it only under Lion, and move all the data to be used under Snow Leopard to a normal, external drive. I could live with that if it offers greater reliability, but it would come at a cost of speed.
The reason there was an incompatibility before was that the drivers (installed on the drives when created) were re-written. The new drivers were not recognized properly in the old Mac OS, and that caused problems.
No one (except possibly some developers under non-disclosure agreement) knows when or if there will be a re-write of the RAID software, or whether there will be incompatibilities or Bugs. Apple in not very forthcoming about when a change is a major one, and when it is just cosmetic.
So the best advice is to let someone else step on those land mines, and wait to see what the Buzz is before you rush to install. Only those who MUST have those new features should be installing on Day 1.
For my piece (or peace) of mind, I would
Invest in SoftRAID 4 : it can convert from Apple RAID to theirs and is a better RAID utility; and see what their support says about Lion and when they will have their own product fully tested and working with the shipping version of Lion. Too often things looked good and ready and yet last minute changes get snuck in and lack of communication and sharing goes on.
Partition tables change. I don't even believe in upgrading over an older OS, I do find reformat with the new OS makes sense, can make its changes, install, and then import/migrate the old files I need, if any, after it is up and running and works. And know that nothing from the old OS or old sytem played a role.
For data, there is good reason to rebuild your array with Lion. I use a new OS as time to replenish and replace drives, and use the old drives as backups. (and always have mulitiple backup sets and clones of volumes).
People learn, the hard way, things like "you can't install or boot Snow Leopard off a Leopard created array" - an array in one case that had multiple partitions, one for each OS. You could do so if you created the array partitions with Snow Leopard though.
Tiger was the first time that OS X arrays were equal or better than OS 9 built, was 10% performance boost over Panther, with the limitation that Tiger's were not backward compatible and would not mount under Panther.
Every new OS has brought changes to Apple Mail and other files, so sharing home folder library and prefs was never really supported or a good idea.
Applications can sometimes do the same and change format, once opened and saved under a new application, or having to Save/Export under old format. (FinalCut Pro X anyone?)
Large storage arrays need to be as OS independent as possible, and one vote of confidence for Hardware RAID controllers, except almost certain to have to upgrade drivers, dropped support for some, firmware updates even are always real recurring and possibilities).
Thank you both for your further explanations, though I'm afraid a fully 'Correct Answer' won't come until Lion is out and I try it out, if I try it out.
I think I'll use a recreated RAID with Lion under Lion only, like I said in my last post, but after others have stepped on any land mines.
SoftRAID seems like a great alternative to an Apple RAID, but a bit too expensive for me, at the moment. I'm not using the RAID for any professional work.
I was also planning on getting a new backup drive when the time comes, so I can keep my current one as an extra backup. I'll still have to boot Snow Leopard sometimes for PowerPC code and the like, but I guess as long as I'm not reading or writing from a RAID it shouldn't be a problem.
Thanks again!
SoftRAID will do more: scan for bad sectors when the system is idle; alert if there is an I/O errror, which Apple doesn't do; support for SSD; very flexible RAID partitions you can create/delete/add without touching other partitions.
For mirror RAID, I would never use Apple's and most people never consider 3-drive mirror (but they want RAID5 which is terrible).
So it is a better disk partitioning tool, good for zeroing drives, and even if you never even used any arrays.
The support is priceless, of course!
I do use SoftRAID btw - like the driver and program - works well. However, my Lion installer is stuck at the grey screen 'cannot install Lion to a RAID volume'. Visiting the Apple support site suggests creating a recovery HD before installing (but install has started on my machine and will not revert to Snow Leopard as it promises when I click the restart button). So there you are. No server, no Lion, no Snow Leopard, no dice, grey screen.
And the other interesting point is that the link on Apple Support to create a recovery HD is now a '404' error.
Nice.
My Macs have all upgraded nicely (good job Apple) - but if you are booting from a RAID array I'm afraid you will need to create a recovery disk first (search the internet for that procedure) and then proceed to install Lion _without_ a recovery HD - which apparently means _no_ firmware password, _no_ filevault encryption and so on to protect your server (disappointing).
I am working through this now. It is frustrating. Sure I will get there but this has been just as much pain as every other server upgrade (Okay well Leopard from Tiger possibly hurt more than this - so far).
I understand Apple also saying it's a 'server for everyone' but 'everyone' does include people who seriously think that having a mirrored boot volume is kind of sensible. I am disappointed by the lack of support for this out of the 'sandbox'. And pulling support pages is a disaster. Now I have to 'Google' to find a solution - oh the irony!
Anyway if I succeed I will re-post/edit and let you know what happens. Just thought this would add some more background to the issue.
ARS Technica has a good article on how to build an Emergency Startup Disk for Lion. I am working through that now to rescue my server that is stuck in an endless Lion install loop.
Luckily I have a spare mac mini that was not yet upgraded (you need the downloaded package from the App Store - don't install it before you build the ESD if you have a RAID array - you need the files in the package).
It also mentions on the ARS site that Apple may be offering the ESD as a USB dongle later this year. Not sure how reliable that is - but it would take some of this pain away.
And perhaps they'll figure out a way to allow you a mirrored boot drive and Lion at the same time. One can dream ...
All good links apart from the first at Apple that has been pulled and cannot be reached. Searching on their site it seems all reference to creating a bootable external disk is gone.
I put some parts of Windows Boot Camp related items into one thread:
Lion Boot Camp Windows Migration Assistant Recovery
Lion Recovery Drive Partition, DVD
This seems to cover what HT4713 (404) may have and been superceeded
OS X Lion: About Lion Recovery
create a startup disk for Lion
Might want to RSS or check the Recent Changes:
PS - good write up
Thank you all for this discussion. I also have a 2008 Mac Pro with a 3-disk array. (I just couldn't help myself from adding that third disk to see if it would make any improvement.) I spent most of Wed. and this morning attempting to install Lion on my raid 0 both with and without SoftRaid and without any success. It installed on a single drive on my Mac Pro and on my MacbookPro fine, but not on a raid. I've suddenly decided that everyone who says you shouldn't be booting from a raid is right. I took the plunge on an 80-gig SSD (good deal on Amazon) and that will be my boot drive. Data will remain on my raid.
I worked this through with SoftRAID. (Refer to their manual if you need full instructions). You need to split your RAID mirror (giving you a backup drive in case anything goes wrong). Convert both disks to non-RAID Apple Disks/Volumes. The you should be able to install Lion on the primary disk and boot from it. Once install is complete go ahead and use SoftRAID to reconstruct your SoftRAID volumes and mirror.
Don't get me wrong - SSDs are brilliant. I use one in my MacBook pro and it flies. But depending on how heavily you use the server features of OS X should dictate the SSD you buy (SSDs require overprovisioning and a decent controller to prevent wear damage - servers are notorious for having lots continuously changing files like logs) - and you should still have a backup copy of the SSD in case it fails.
The purpose of mirrored RAID is not any extra read-speed gain (although it is nice if you get that) but rather that if your primary disk fails you have a redundant online copy that will immediately take over and save your hide.
SSDs are more reliable but if your boot drive dies you still need a backup. And if you dont use mirroring to a second SSD you'll need to recover your boot drive from ... a mechanical drive?
Snow Leopard RAID 0 in Lion?
