Considering SSD software RAID0...

[Dreamail]

Thanks for all answers. One can always learn something valuable from this excellent group of posters!

In the case of GUID partition tables, it's duplicated on both the front and back of the disk. So it has a duplicate, which helps in the event damage does occur. It offers the ability to salvage the drive, and access the data on it.

This is interesting!
Is this part of any normal Softraid RAID 0 setup?
And which software can use that duplicate GUID partition?


As you can guess from my question I am considering putting 2 SSDs via RAID 0 in my Mac Pro using as boot and main data drive. (With extra TimeMachine HD plus off-site backups of course.)

Since cost should be minimal (the drives are expensive enough) I am considering using the OSX's built-in Softraid rather than buy a dedicated RAID card. At this point I'd rather get a bigger SSD than a RAID card.

Yet I'm not sure if this setup wouldn't be too fragile compared to a normal single drive setup.

With a striped RAID my main worry would be recovering in case of a total drive disaster.
Also the likelyhood of the GUID data getting corrupted during 'normal' crashes, hard-reboots or power failures.

With a single drive you can always use some sniffer software to poke into bits on the platters. With a striped drive stuff's all over the place and sniffing for important information (which wasn't yet backed up) would seem to be a lot harder.

 

[Tesselator]

I like that

LOL That's a good one!



kidding

Hey! I represent that!

 

[AppleWorking]

Hey! I represent that!

 

[Tesselator]

Yet I'm not sure if this setup wouldn't be too fragile compared to a normal single drive setup.

Naw, less fragile over all I would imagine. I think SSDs are less prone to total catastrophic failure than HDDs with all their moving parts.

With a striped RAID my main worry would be recovering in case of a total drive disaster.
Also the likelyhood of the GUID data getting corrupted during 'normal' crashes, hard-reboots or power failures.

That's what back-ups are for. But I wouldn't spend too much time worrying about it. Even with HDDs in a RAID0 the likelihood of such things happening are extremely slim!

With a single drive you can always use some sniffer software to poke into bits on the platters.

Sometimes. I wouldn't even say "usually". Seldom better describes it IMHO. And again, who cares if you have backups from just a few hours earlier? Just restore and forget about it. That's the whole idea of a back-up.

 

[nanofrog]

Is this part of any normal Softraid RAID 0 setup?
And which software can use that duplicate GUID partition?

Yes, if you mean the OS.

Maybe if it's a add-in SATA card (depends on the drivers), but not usually the case if it's under a RAID card (Apple's RAID pro would be the only possible exception).

But in the case of OS X using the board's SATA ports, it is, and applies to both single drives and arrays in OS X. It's not the actual data, just a duplicate copy (backup) of the Partition Table (pointers to the location of the data). It's there to help recover in case an illegal operation occurs to the Partition Table. If it's a normal operation, the changes will be duplicated. It can't help cover bad sectors though. That's something else (remapping, and the data being salvaged isn't certain).

In any event, you want to have a good backup system in place, as Tesselator recommended. It helps with the various failures better than any other method. There really is no substitute. Only additional useful aids.

As you can guess from my question I am considering putting 2 SSDs via RAID 0 in my Mac Pro using as boot and main data drive. (With extra TimeMachine HD plus off-site backups of course.)

Since cost should be minimal (the drives are expensive enough) I am considering using the OSX's built-in Softraid rather than buy a dedicated RAID card. At this point I'd rather get a bigger SSD than a RAID card.

It would be easy enough to set up, and you won't need a RAID card for OS X. The oddball issue is for Windows, as I'm not aware of a basic SATA card that can boot OS X (EFI firmware). Only a couple of brands of RAID cards are EFI boot capable. So if you're on a budget (or want the simplest method to install Windows), just use a single disk, as it cannot be placed on an array created by OS X.

Yet I'm not sure if this setup wouldn't be too fragile compared to a normal single drive setup.

With a striped RAID my main worry would be recovering in case of a total drive disaster.
Also the likelyhood of the GUID data getting corrupted during 'normal' crashes, hard-reboots or power failures.

No, it won't be fragile. If anything, it's a bit more stable, as there's no moving parts that can fail.

Again, a good backup will solve your worries. Now you can still loose a small amount of data, depending on the time of the most recent backup to the time of the failure, and what you were doing during that time. You'll need to figure out the best scheduling for your backups (minimal data loss, if any at all).

Of course, with RAID, a UPS really ceases to be an option, as it covers you during a write operation occuring during a power failure. You can save it, then shut down.

There's still a few odd (rare) possibilities, and that's primarily the PSU in the system. If it fails, there is no redundant unit, and when they do go, they can take other stuff with them, such as CPU's, main boards, memory, drives... Again, this is where the backup bails you out.

So the moral of the story is, if you're running RAID, use backups + UPS.

With a single drive you can always use some sniffer software to poke into bits on the platters. With a striped drive stuff's all over the place and sniffing for important information (which wasn't yet backed up) would seem to be a lot harder.

That's what the backups are for. Never leave it to data recovery software or services to obtain your data. The backup is more effective, and way cheaper if you ever have to use a data recovery service.

 

[gugucom]

Also not to forget!!! Switch off defrag for any SSD you use in your system or it will quickly kill your SSDs by exceeding the maximum refresh cycles. Leave it to the controller to organize the SSD. Any interference from the OS will make things dramatically worse.

 

[Tesselator]

Also not to forget!!! Switch off defrag for any SSD you use in your system or it will quickly kill your SSDs by exceeding the maximum refresh cycles. Leave it to the controller to organize the SSD. Any interference from the OS will make things dramatically worse.

Is there such a switch in OS X? Is that new in SL or something?

 

[nanofrog]

Is there such a switch in OS X? Is that new in SL or something?

I presume it was made as a general statement, though particularly applicable to Windows. Especially since he's been working on getting an array set up with a pair of SSD's specifically for Windows.

 

[ungraphic]

Is there such a switch in OS X? Is that new in SL or something?

+1

I've always thought OS X had 'built in' defragmentation that ran in the background.....if so, how do u turn it off?

 

[Dreamail]

Thanks again to everyone for the really helpful answers!


If there is a 'no defragmentation' switch in OS X, that would be good to know where it is. But I haven't heard there is one.
But I'm also not sure to what extent auto-defragmentation is done in the background.

Someone else mentioned to be careful with a software RAID 0 as one cannot boot into Windows with it. But that's no concern as I don't intend to do that, I'd only run XP via VMware Fusion.

 

[TheStrudel]

As far as I'm aware, auto-defrag happens either on reboot, or during the periodical maintenance scripts OS X runs. There is a way to disable it, but I can't remember what it is. Of course, I heard that back in the Tiger days, so I'm not sure what it is now, especially in 10.6

 

[gugucom]

Someone else mentioned to be careful with a software RAID 0 as one cannot boot into Windows with it. But that's no concern as I don't intend to do that, I'd only run XP via VMware Fusion.

Actually its a bit different. When you have a software array in OS X it will prevent you from installing a Windows drive. Once it is set up it isn't affected by the presence of an array. So booting into Windows with RAID prsent is not a problem per se.

 

[GeneralAntilles]

As far as I'm aware, auto-defrag happens either on reboot, or during the periodical maintenance scripts OS X runs. There is a way to disable it, but I can't remember what it is. Of course, I heard that back in the Tiger days, so I'm not sure what it is now, especially in 10.6

It happens on-the-fly based if a number of conditions are satisfied. See the section at the end of this article for details.

 

[Tesselator]

Actually its a bit different. When you have a software array in OS X it will prevent you from installing a Windows drive.

No, you can install a windows drive and even do the split partition thing. Either one will work just as if there were no RAID0 connected at all. The one caveat is that the drive you plan to format or partition needs to be in Bay1. Bays 2 ~ 4 and the two spare SATA ports can have any type or combination of RAIDs or single drives you like.

And also just like he said, once you create and boot into Windows none of the RAIDs will mount in Windows. They appear as unprepared, unwritable, unreadable, single drives.

Also RAID (including 0, 10, and JBOD) member drives can be shuffled around without any trouble. So if you're RAID is currently in Bays 1, 2, 3, and 4 for example, you could easily put the Bay1 drive in the ODD area and the RAID would continue to function as if nothing had changed.

 

[Macinposh]

Also RAID (including 0, 10, and JBOD) member drives can be shuffled around without any trouble. So if you're RAID is currently in Bays 1, 2, 3, and 4 for example, you could easily put the Bay1 drive in the ODD area and the RAID would continue to function as if nothing had changed.

Wha?
So,I can take the drive from the bay1 and shove it to the ODD area and connect it to the mobo´s sata slot and the raid will still work??

 

[gugucom]

http://www.intel.com/support/chipsets/imsm/sb/CS-025783.htm

There is also a general issue with Intel RAID chips and Vista installation which was dealt with by some later software releases. I am experiencing something like this with my Intel IOP333 in my Areca card now.

If you use Intel matrix storage manager you need to use versions higher than 7.0. The current release it 8.9.

 

[nanofrog]

http://www.intel.com/support/chipsets/imsm/sb/CS-025783.htm

There is also a general issue with Intel RAID chips and Vista installation which was dealt with by some later software releases. I am experiencing something like this with my Intel IOP333 in my Areca card now.

If you use Intel matrix storage manager you need to use versions higher than 7.0. The current release it 8.9.

The newest release is stable, and I'd recommend using it.

The article refers to the ICHx model in the chipset though. The ARC-1210 is a separate device, and I've not seen any instances of collision with the ICH10R on the board I'm currently using (different device addresses do seem to do their job in preventing such issues).

 

[gugucom]

The newest release is stable, and I'd recommend using it.

The article refers to the ICHx model in the chipset though. The ARC-1210 is a separate device, and I've not seen any instances of collision with the ICH10R on the board I'm currently using (different device addresses do seem to do their job in preventing such issues).

Customer reports at Intel suggest that 8.9 is connected with unexplainable drive failures. Intel have said they recommend 8.8 and 8.9 only for Win7.

I don't know what is wrong with my IOP333, but it drives me nuts and the issue reads exactly like the one Intel had with the 5000 chipsets and the 7.0 versions.

 

[nanofrog]

Customer reports at Intel suggest that 8.9 is connected with unexplainable drive failures. Intel have said they recommend 8.8 and 8.9 only for Win7.

I don't know what is wrong with my IOP333, but it drives me nuts and the issue reads exactly like the one Intel had with the 5000 chipsets and the 7.0 versions.

I've only single drives attached to the ICH10R (3x 1TB Caviar Blacks for backup, and a 300GB Velociraptor meant for OS X). I've not had any problems. But it is running Win7 RC. I found it stable enough to dump Vista. Which occured as a result of MS not liking my reinstall count, and gave me the "Illegal Copy" crap. Needless to say, it pissed me off, as even after I did the phone verification, updates where still disabled.

But when you select the OS, I don't recall it offering one of the Win7 versions. I'll have to go to Intel's site and take a look at that (curious, and what to confirm), and check out the user/customer posts/reports as well.

 

[gugucom]

I have not tried Win7 yet because I did not intend to buy another Windows down the road. I may be an idea for testing if the bug is there as well.

 

[nanofrog]

I have not tried Win7 yet because I did not intend to buy another Windows down the road. I may be an idea for testing if the bug is there as well.

I'll check it out later this evening, and see what I come up with. You've definitely made me curious about this.

 

[gugucom]

I have checked out Win7-RC and rEFIt shows two images. One is rejected out of hand. It looks funny like a three dimensional symbol for Windows. That is probably for 64EFI only. The other one looks conventional but has the usual bug that makes my EFI32 freeze. Multiple load variables that the boot loader can't handle. I may have a chance to modify the iso to take the variables out, but that is a slim chance.

 

[nanofrog]

I have checked out Win7-RC and rEFIt shows two images. One is rejected out of hand. It looks funny like a three dimensional symbol for Windows. That is probably for 64EFI only. The other one looks conventional but has the usual bug that makes my EFI32 freeze. Multiple load variables that the boot loader can't handle. I may have a chance to modify the iso to take the variables out, but that is a slim chance.

It also sounds like a lot of work, for something that should be rather simple.

Man, Apple's reluctance to release 64bit EFI has really raked you over the coals on this.

Any update on the possible swap to a newer machine ('08 IIRC)?

 

[Tesselator]

Wha?
So,I can take the drive from the bay1 and shove it to the ODD area and connect it to the mobo´s sata slot and the raid will still work??

Yes sir. Confirmed it myself. The location doesn't matter at all. You can take them all out and put them all back in different locations including the two SATA connectors under the fan, and it will all just work. Nice huh?!?!

 

[gugucom]

It also sounds like a lot of work, for something that should be rather simple.

Man, Apple's reluctance to release 64bit EFI has really raked you over the coals on this.

Any update on the possible swap to a newer machine ('08 IIRC)?

I found a solution to eliminate the undigestible variables and I'm just testing it.

http://jowie.com/blog/post/2008/02/...t-from-Vista-x64-DVD-burnt-from-iso-file.aspx

My previous method may have been flawed. I used to simply extract one straightforward image from the disk by use of nLite. I am aware that this has changed other aspects of my bootable installation disks. Among the noticable changes was the loss of the repair option, which I missed dearly.

So perhaps Howie's way is better for me. I had some difficulties to heck his description but now it appears that I have got it.

EDIT: I'm installing Win7-64 on my SSD RAID0!!!!!!!!!!!!!!!!!!!!!!!!!!

It also told me that my BIOS is not suitable but at least it started to install. It broke off in the last minute when it should have restarted the computer. Perhaps I will be able to work around that issue. I'm starting it again and will manually shut down if that is the only way to make sure it restarts.

keep the fingers crossed, please puuuuuleeezzzzeeees.