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gt
06-14-2001, 12:10 PM
OK
Miles2 installed and associated software installed and upgraded.
18 Gig 10K Cheetah installed in bay.
Twisted pair ribbon installed. Ready for softraid. WHERE'S THE HD?!
(Insert twenty minutes of scrambling and reading) Deep breath. Sit back and assess........ CRAP! Dummy! You gotta plug in the juice! Embarrased at self.

Now, formatting.
I will be ordering another Cheetah sooner than I thought I would be able to. In the interim:

1) I'm reading contradictory advisements from Conley. In some of their documentation is sounds (to me) as if mirroring and / or striping can be set up at any old time without losing data. In the program itself, it seems to warn that existing data will be lost from a volume if if RAID is set up after the fact. Which is correct?

2) It also sounds (to me) as if matching size volumes across two disks can be treated differently. i.e. a 4 gig partition can be set up to mirror, and a 6 gig partition can be set up to stripe on the same disk. Is that right? (Is that what RAID 5 is?) I've been over and over these forums and don't see any discussion of it so I'm thinking that's not possible or adviseable. What's the skinny?

3) Is it OK to go ahead and set up partitions as Mirrored and / or Striped on the existing Cheetah and use the disk without the second disk being installed for a while? Or will that screw things up?

Thanx for any guidance you pholks can give.

Greg

dragon_x
06-14-2001, 01:49 PM
1) Not sure about Conley. For SoftRAID you will lose any data when formating. You can convert a drive or update a drive to SoftRAID without losing data, though.

2) This is not RAID -5. Here is an example of what I think they are saying
You have TWO 18GB drives. You could
a) format them as single drives with whatever utility you wanted
b) Stripe them (RAID-0) for a single 36GB fast drive
c) mirror them (RAID-1) for a single 18GB drive that is more robust.
d) Stripe say 9GB on each drive for a single 18GB fast drive and with the remaining 9GB on each drive set that up as a mirror.

I think SoftRAID will allow you to do ALL of the above. I have never run a MIrrored RAID setup though. I have set up multiple stripped partitions with SoftRAID - usually I will do a 2 ~4GB boot partition (about 2GB from each drive) and then use the rest for data.

RAID-5 normally uses a set of 3 drives. Two are striped (for speed & size) and then the third drive is used as a 'parity checker' of some sort. I guess this is based on the theory that any given time you will only loose one drive - or half your data. The 'parity checker' drive uses the remaining data on the good drive and its own data to keep the system going. I think I'm mostly right on this. To my knowledge there are NO software RAID-5 solutions (Mac or PC). SoftRAID has been 'working' on such a system for a long time. They have fairly high standards so they wont release anything until its bullet proof. There are hardware RAID 5 solutions but those are mainly for servers and not Macs. System X may change this though. It would probably to expensive for the average pro anyway.

3) You can use the drive, but you do need more than one drive to setup a RAID 0 or RAID 1. When I run with single drives - I simply use the Apple drive setup. It works great. I only use SR when running with RAIDed drives or drives (rare) that do not work with the Apple drivers. Again you will lose data when you go from a single disk to multiple disks.

------------------
So long and thanks for all the fish!

MacMikester
06-14-2001, 07:04 PM
SoftRAID is capable of RAID 0, RAID1 or any combination, often called RAID 0+1, not RAID 5. What you actually stripe or mirror are logical volumes, not hard drives, so you can stripe or mirror, for example, a 4G volume on one 18G drive with a single 4G volume which takes up all of a 4G drive. You could then mirror that striped volume on an 8G volume on the 18G drive, for another example.

SoftRAID will allow you to create new stripes or mirrors from existing volumes without destroying the data on the current volumes. This takes time but is done as a background process and you can use the volumes while the new arrays are being built.

It makes no sense to stripe or mirror two volumes on the same drive since you gain no I/O speed or data redundancy in the face of the drive failure. Your most efficient, fastest and least error-prone arrays are set up using volumes on identical drives. This way I/O rates are the same for all members of the array. Symmetry is the rule in reliable arrays.

SoftRAID is an excellent driver for single drives as well as arrays. You can set up your current Cheetah any way you like now and create a stripe and/or mirror with the second Cheetah when you get it.

Regards

gt
06-14-2001, 08:13 PM
Thanks for the info fellas-

When I started my upgrade project I thought I would have to dedicate the disks one way or the other. The ability to have both striped and mirrrored volumes on the same two disks really expands my options.

There's one problem, though: The ability to have both striped and mirrrored volumes on the same two disks really expands my options.
More choices and planning to get it juuusst right. Ugghhh! http://www.macgurus.com/ubb/confused.gif

I just ordered the other disk today- I don't want to wait for the opportunity to mess up two disks at once! http://macgurus.com/infopop/emoticons/icon_biggrin.gif



[This message has been edited by gt (edited 14 June 2001).]

magician
06-15-2001, 02:58 AM
ok, careful now: genuine "RAID 0+1" is not yet available using SoftRAID. This would entail the mirroring of a striped volume. If you actually try to do it, you will eventually realize it is not yet feasible.

SoftRAID does pure RAID 0, and RAID 1. Only. We discuss them on our RAID FAQ on the main site.

MacMikester
06-18-2001, 12:04 AM
Sorry gt, the SoftRAID documentation makes it sound like RAID 0+1 is already possible. "or any combination" is a quote from the documentation.

magician
06-18-2001, 01:49 PM
right.

it's been "on the drawing board" for quite some time now.

http://macgurus.com/infopop/emoticons/icon_smile.gif

gt
06-18-2001, 04:09 PM
I'm not normally so dense, although some who deal with me will disagree emphatically.

I think my obtuseness is caused by my confusion over the use of the term "volume".

Does "volume", when discussing RAID, refer to the entire HD, or to individual partitions set up on HDs? In the SOFTraid window, under "volumes" it lists the partitions I have set up on various HDs.

Conley's use of the term "volume" in their pdf manual seems to change from page to page. Seems? Heck, it DOES change from page to page.

I have (or will have shortly, when the second, B/O'd, 18 gig,10K Cheetah arrives) two identical HDs on a Miles2 card.

I do not desire to, if I understand Magician's comment, stripe two existing mirrored volumes, or vice-versa.

On to the basics:

(For simplicity in this discussion) I will set up each drive, identically, into two partitions of 9 gigs each which I will call A and B on each disk.

Can I take "disk 1, partition A", and "disk 2, partition A", and set them up as Raid 1 (mirrored)? I'm sure the answer to this is yes.

Now---Can I take "disk 1, partition B" and "disk 2, partition B" and set them up as RAID 0 (striped)?

If each of the partitions is indeed a volume (and they show up as separate volumes in the SOFTraid window) it seems the above is possible.

If I just don't get it, kick me in my butt and send me on my way.

Thanks for your patience and expertise.

Greg





[This message has been edited by gt (edited 18 June 2001).]

jorge
06-18-2001, 08:06 PM
Softraid can't do much until Apple releases the driver kit for Mac OS X.

j

Louie
06-18-2001, 09:34 PM
Volume is sometimes refered to as Partition. Volume is a partition that can be mounted. There are also driver partitions that can't be mounted.

magician
06-20-2001, 03:16 AM
Greg, you get it just fine.

you can do exactly as you propose. SoftRAID was designed to work that way.

I myself prefer to keep thing simpler, and use two drives for a mirror, and separate drives for a striped partition, but that should not deflect you: Mark James, the honcho at SoftRAID, runs his machines exactly as you have outlined.

Volumes are logical partitions that you create to hold data.

As Louie mentions, not all partitions are volumes. Driver partitions are not considered volumes, for example, but they are definitely partitions.

Data partitions are certainly partitions, but since they mount on the desktop, and can be written to, and read from, and can store information, they are volumes.

as you intuitively grasp, you can create partitions on drives, which are nothing more than logical divisions of media, meaning organization of physical space on your drive platters, and if they are not used to hold data, then they are not properly considered volumes.

only partiions which hold operator data are volumes.

you can partition drives, and yes, combine partitions in member striped partitions, or mirrored partitions: the act of combining them and using them for data storage, mounting them as a logical unit on the desktop, makes them volumes.

cool?


http://macgurus.com/infopop/emoticons/icon_smile.gif

dragon_x
06-20-2001, 09:00 AM
Conley's use of the term "volume" in their pdf manual seems to change from page to page. Seems? Heck, it DOES change from page to page.

This is to confuse us, so we can spend big $$ on 'consulting fees'! http://macgurus.com/infopop/emoticons/icon_wink.gif

magician
06-20-2001, 11:47 AM
or get the same info free here on the Gurus upgrades forums.


http://macgurus.com/infopop/emoticons/icon_biggrin.gif

gt
06-21-2001, 02:00 AM
Magician-

VERY cool!

Thank you for once again cutting through the (my?) BS. http://macgurus.com/infopop/emoticons/icon_biggrin.gif

Greg

[This message has been edited by gt (edited 21 June 2001).]

jpmacman
06-29-2001, 03:36 PM
I'm looking to setup a medium capacity G4 Server using ATA Drives, an additional PCI Card, and SoftRAID. What I'd like to do is setup 4 identical 75GB drives for Data. I was going to stripe 1,2 and 3,4. I would then like to setup Array 3,4 to mirror Array 1,2. This way I'll have one Phat volume of 150GB for space that's mirrored. The server will get dumped to tape weekly for backup, but I'd like it also to be somewhat realtime in case soemthing happens.

My questions is can this be done with SoftRAID. It would seem so . . .

John Pinnell
JP Consulting
St. Louis, MO

MacMikester
06-29-2001, 11:12 PM
What you are describing is RAID 0+1 and is not yet capable with software RAID. SoftRAID is reportedly developing this feature. You cannot yet mirror a striped array or use a striped array as a mirror.

Regards

Santilli
06-30-2001, 04:53 PM
That's why I had those error messages, and had to constantly rebuild the mirrored volume....and had errors on the raid 0 volume every once in a while...


gs