Somewhat OT - How to RAID

ejl10 · Post by **ejl10** » Fri Nov 14, 2003 12:30 pm

Well, I've never had drives in a RAID configuration before, so I'm wondering if there's a way to do what I want to do. Basically, my new motherboard supports SATA RAID 0 and 1. I'd like to eventually get two Samsung Spinpoint 160's going in RAID 0 (striping not mirroring), but don't want to spend the $$ on it today. Is there a way I could pick up one drive now, load it up with my OS and data, and then at some point in the future add the other one and convert the data into the RAID 0 stripes?

As I re-read my question now it seems like a long shot. But I figure it's always better to ask. My WD drive is way too noisy, and I'm looking for a "stepping stone" approach to reach my ultimate goal without losing any data.

Thanks,
Emmett Lyman

Jan Kivar · Post by **Jan Kivar** » Fri Nov 14, 2003 12:46 pm

Only if You have a PIV system, which has ICH5-R southbridge on the motherboard (some i865/i875-based boards have it). It can build RAID0 array from existing data.

With all other RAID controllers (AFAIK...) the drives are erased when You do a RAID0 array. Nearly all controllers can build RAID1 array with existing data.

Or were You meaning RAID1 after all? RAID0 has no added reliability. Actually, RAID0 lowers reliability. Unless You need RAID0 (process huge raw video files etc.), You're better off running two drives independently. Or just one drive, if You don't need 300 GBs of space...

Cheers,

Jan

ejl10 · Post by **ejl10** » Fri Nov 14, 2003 1:03 pm

That's pretty much what I expected (RAID 0 was correct). I've got an MSI KT6 Delta motherboard with a Via VT8237 SATA controller. Basically, I wanted to RAID because I've never done it before. Just an experiment (since the mobo supports it), and not much more

. If I can't do it easily, it loses it's appeal!

Thanks for your input,
Emmett Lyman

scalar · Post by **scalar** » Sun Nov 16, 2003 7:09 am

Expandability without reformatting is possible with RAID, but probably not with what is on your motherboard. That is reserved more for the higher-end RAID cards that cost $500 or more just for the RAID controller.

You would likely need an external drive to hold data while upgrading the RAID array your motherboard supports. The drive array would need to be formatted and striped, and then you'd recopy the data back from the external drive to the RAID array.

Archeon · Post by **Archeon** » Sun Nov 16, 2003 5:31 pm

Jan Kivar wrote:Only if You have a PIV system, which has ICH5-R southbridge on the motherboard (some i865/i875-based boards have it). It can build RAID0 array from existing data.

Jan,

I've got an Intel P4 i865 PERL motherboard, and I 've also been thinking in doing a RAID setup. Do you mean it would be as easy for me as to put another HD of the same type and size next to the one I'm using now and the RAID array would build itself? If so, that would be extremely cool and convenient!

Thanks !

scalar · Post by **scalar** » Mon Nov 17, 2003 12:36 am

It won't "just build itself". There's some sort of BIOS boot tool that you use to create the array. And in the process it will destroy any existing data unless you back up the data first so you can copy it back after the RAID array builds.

On the topic of volume growing, it needs to be set up in a weird manner on the controller to actually work. And it's not as simple as having a RAID-card that can do it, because the OS needs to support volume growing, too.

Jan Kivar · Post by **Jan Kivar** » Fri Nov 21, 2003 11:38 am

Archeon wrote:
Jan Kivar wrote:Only if You have a PIV system, which has ICH5-R southbridge on the motherboard (some i865/i875-based boards have it). It can build RAID0 array from existing data.
Jan,

I've got an Intel P4 i865 PERL motherboard, and I 've also been thinking in doing a RAID setup. Do you mean it would be as easy for me as to put another HD of the same type and size next to the one I'm using now and the RAID array would build itself? If so, that would be extremely cool and convenient!

Thanks !

Sorry for the delay, I've been rather busy with my studies...

You can migrate your existing installation into RAID0 array, if You have a board that has the ICH5-R southbridge. [I looked at Intel; there are four versions of your board, only two have RAID capability.]

You must have Win2k or XP to make the RAID0 array, and You must do it within Windows. You will need "RAID edition" of IAA (Intel Application Accelerator).

Here's a link to Intel site: What is the RAID migration feature?

Cheers,

Jan

ejl10 · Post by **ejl10** » Fri Nov 21, 2003 12:36 pm

Well, I decided to just bite the bullet and buy two drives at once. Despite the very clear warnings about reliability, I've always wanted to try RAID0. I know that hard disk access is, in a few situations, a system bottleneck, and I'm curious to know firsthand how it will effect performance. Plus, 320GB of quick storage will be nice

I'll be careful to backup everything often!

Thanks for the help,
Emmett Lyman

Ana · Post by **Ana** » Fri Nov 21, 2003 1:07 pm

ejl10 wrote:Well, I decided to just bite the bullet and buy two drives at once. Despite the very clear warnings about reliability, I've always wanted to try RAID0.

I think the warnings about reliability are a bit overdone; the only pro-
blem with RAID 0 reliability is, that if one of your HD's explode, you lose
data from both volumes, the other volume being rendered useless without
it's pair. In 15 years of active computing, I've had one faulty hard drive,
and that was a notorious Seagate Bigfoot. Everyone I know who had one
of those have told me they failed after a year or two.

A RAID 0 setup with two 120gb hard-drives is faster and more reliable than
a setup with a single 240 gb, because if one of the disks fail, you still got
one working 120 gb drive

In normal home computing, it's worth the risk. In a server, use 0+1 and
go buy two more disks (and an external RAID card)

ejl10 · Post by **ejl10** » Fri Nov 21, 2003 2:03 pm

Well, I've jsut received two of the Samsung 160GB SATA drives, so we'll see how it works. I've had "catastrophic" data loss on my PC a few times (it was never really catastrophic!), so I'll be sure to back it up this time. I like the Netdisks, but they're too expensive. I'll probably put my current disk in a USB encolsure instead.

Thanks for the advice,
Emmett Lyman

grandpa_boris · Post by **grandpa_boris** » Fri Nov 21, 2003 4:25 pm

Ana wrote:In a server, use 0+1 and
go buy two more disks (and an external RAID card)

RAID0, aka striping, is used to increase data access speed. if all one needs is more space attached to a single windows drive letter, then spanning (allowing the storage volume to occupy more than one disk, but not interleaving the data blocks) is just as good a solution. i don't know of any hardware controller solutions that do spanning, but i haven't looked too hard, either.

if all you want to do is simple spanning, RAID0, RAID 1 (no fast resync), or RAID 5 (no log), you don't need an external RAID card if you are using win/2k, 2k3 or xp. simply convert your disks to "dynamic" and get all of that functionality in software. the advantage is that you don't get the disks tied to the hardware RAID subsystem. the same disks attached to a different motherboard or controllers, with or without native RAID capabilities, will still give you access to your data. a while back tom's hardware had an article describing how to do this. there are also several industrial strength software RAID packages for windows, but they'll cost you money.

ejl10 · Post by **ejl10** » Sat Nov 22, 2003 8:35 am

Grampa_Boris,

Thanks for that article. That's great information; I never realized that Windows was capable of doing that. I'm definitely going to keep that in mind for next time, but for this particular exercise I plan to have Windows installed directly on the array drive, and Tom's says that this can't be done by the software alone. It looks like that would be an excellent way to build a Swap drive array, if anyone is planning such a project.

Thanks for the good info,
Emmett Lyman

Ana · Post by **Ana** » Sat Nov 22, 2003 1:33 pm

Software RAID is scary. Just one byte away from a total disaster :I

grandpa_boris · Post by **grandpa_boris** » Sat Nov 22, 2003 4:04 pm

ejl10 wrote:I plan to have Windows installed directly on the array drive, and Tom's says that this can't be done by the software alone.

the version of RAID software that is bundled with windows is artificially limited. the full version is a lot more feature-rich, but isn't free. tom's review seems to say that you can't build a RAID 0 or 1 volume at windows install time and install windows to it. it's entirely possible, but tom's doesn't always get their facts quite right. i will verify tom's assertion and post the facts.

grandpa_boris · Post by **grandpa_boris** » Sat Nov 22, 2003 4:16 pm

Ana wrote:Software RAID is scary. Just one byte away from a total disaster :I

a properly implemented software RAID isn't fragile and it takes a lot more than a single byte failure to lose data. but this is straying way, way away from relevance to this forum. if you want to discuss this in more depth, you can PM me.

Jan Kivar · Post by **Jan Kivar** » Wed Nov 26, 2003 10:17 am

grandpa_boris wrote:if all you want to do is simple spanning, RAID0, RAID 1 (no fast resync), or RAID 5 (no log), you don't need an external RAID card if you are using win/2k, 2k3 or xp. simply convert your disks to "dynamic" and get all of that functionality in software.

Only server versions have RAID1 and RAID5. The normal OSs have only means to use these arrays, NOT to create them.
There is a crack to have RAID1 and RAID5 in regular XP, but it's not recommended.

One can only boot from SW RAID1 arrays, not from RAID5 and RAID0 (software versions, that is). Even then it is advisable to have both drives/installations in the boot.ini, or otherwise one must physically change the working drive to the place of the broken drive (=swap the cable positions between drives), if the broken drive was the "primary" drive.

Lastly, about creating the RAID array while installing: You cannot do it with software. IIRC it is possible to have a "array creation utility" in the BIOS of the motherboard w/ ICH5-R, so it could be possible to build array BEFORE installing. AFAIK this is limited to some manufacturers and BIOS revisions only.

All "normal" RAID cards/controllers have this array creation utility, the previous chapter relates only to ICH5-R.

Cheers,

Jan

qnliu · Post by **qnliu** » Wed Nov 26, 2003 1:00 pm

Just to echo grandpa's idea, I use software RAID 0 on WinXP pro and feel great about it (2 months so far).

A couple years ago I played with RAID 0 on a highpoint card. As luck have it I had two hard drive (both maxtor) failures in half a year, and lost a lot of data. I gave up on that as soon as the second hard drive failed.

The way I set up my system is like this. I have two 40gb drives of the same model. I convert both to dynamic disks. On both disks I create two simple volumes of 10gb each (these are just like normal disk partitions). My OS is installed on a simple volume on drive A. On the sister volume (drive B) I store norton ghost images of the OS as well as regular backups of email, my docs, etc etc. With the leftover 30gb of space on both drives I make a RAID 0 volume of 60gb. On that I store everything that's also on CD and relatively painless to restore: pictures, music, lots of games...

As you can see, this setup is a compromise. All my OS files are loaded at normal drive speed. My games etc however are loaded at RAID 0 speed (slightly less than 2x according to sissoft sandra). If one drive dies, I can go buy a new one and have tho OS partition restored in half hour or less. Copying the rest of the stuff off CDs will take awhile but at least I have a fully functional computer to use meanwhile.

Anyway, if you have ever experienced the sinking feeling you get when you hear a drive make multiple attempts to spin up or that clicking sound from failure to seek, you'll stay away from a pure RAID 0 setup.

grandpa_boris · Post by **grandpa_boris** » Mon Dec 01, 2003 11:20 pm

Jan Kivar wrote:Only server versions have RAID1 and RAID5. The normal OSs have only means to use these arrays, NOT to create them.

people who know tell me that the disk manager software bundled with win/2k pro and server (not workstation) and win/2k3 has RAID 0, 1 (no fast recovery) and 5 (no log) enabled. XP has only RAID 0 and concatenation. the full-featured version of the product is aimed at the larger servers and costs something like $750.

One can only boot from SW RAID1 arrays, not from RAID5 and RAID0 (software versions, that is). Even then it is advisable to have both drives/installations in the boot.ini, or otherwise one must physically change the working drive to the place of the broken drive (=swap the cable positions between drives), if the broken drive was the "primary" drive.

the issue here is the BIOS-dictated order of scanning for bootable drives. the limitation of a software solution is that the basic OS services have to be loaded to run the parts of the OS that do RAID virtualization. that means the boot image has to look sufficiently like a simple disk to be readable by the BIOS. the recommended configuration is to make a smallish mirrored boot/root volume (C: drive)and install applications and store data on the volumes/"drives" other than the C: drive. this works great for corporate database and file servers, but doesn't match most desktop users' environments (unless they are old unix hackers

).

Lastly, about creating the RAID array while installing: You cannot do it with software.

i forgot to ask my sources about that

.

as far as the unbeatable advantages of software RAID, consider this: if you store your data on a hardware-managed RAID set, moving these disks to another system (or failing them over to another server if the primary server panics) is a major hassle. things are much simpler with the software.

Jan Kivar · Post by **Jan Kivar** » Fri Dec 05, 2003 4:01 am

grandpa_boris wrote:
Jan Kivar wrote:Only server versions have RAID1 and RAID5. The normal OSs have only means to use these arrays, NOT to create them.
people who know tell me that the disk manager software bundled with win/2k pro and server (not workstation) and win/2k3 has RAID 0, 1 (no fast recovery) and 5 (no log) enabled. XP has only RAID 0 and concatenation. the full-featured version of the product is aimed at the larger servers and costs something like $750.

There is no Win2000 workstation, the single-user version is called "Windows 2000 Professional". There are three server versions, Server, Advanced Server and Datacenter Server. Only the server versions have RAID1 and RAID5. As far as I know...

grandpa_boris wrote:
One can only boot from SW RAID1 arrays, not from RAID5 and RAID0 (software versions, that is). Even then it is advisable to have both drives/installations in the boot.ini, or otherwise one must physically change the working drive to the place of the broken drive (=swap the cable positions between drives), if the broken drive was the "primary" drive.
the issue here is the BIOS-dictated order of scanning for bootable drives. the limitation of a software solution is that the basic OS services have to be loaded to run the parts of the OS that do RAID virtualization. that means the boot image has to look sufficiently like a simple disk to be readable by the BIOS. the recommended configuration is to make a smallish mirrored boot/root volume (C: drive)and install applications and store data on the volumes/"drives" other than the C: drive. this works great for corporate database and file servers, but doesn't match most desktop users' environments (unless they are old unix hackers ).

Again, AFAIK the drives will work just fine independently for RAID1 arrays. Same applies to my Promise card: I can pull out a drive, and use it as single. I think that I'd have to rebuild the array if I would put the drive back though. I did try this when I updated my array (not the rebuild part though...).

Feel free to correct me if You have better info.

Cheers,

Jan

grandpa_boris · Post by **grandpa_boris** » Fri Dec 05, 2003 11:34 am

Jan Kivar wrote: There is no Win2000 workstation, the single-user version is called "Windows 2000 Professional".

you are right. i had forgotten that it ended up becoming win/XP.

Again, AFAIK the drives will work just fine independently for RAID1 arrays. Same applies to my Promise card: I can pull out a drive, and use it as single. I think that I'd have to rebuild the array if I would put the drive back though. I did try this when I updated my array (not the rebuild part though...).

you are correct about RAID-1 layout being usable when one of the disks is disabled. mirroring was designed specifically to address that issue. in a 2-way mirror both mirrors have all blocks of the logical volume. i was referring to RAID0 and RAID5. on them the blocks of the logical volume are striped/interleaved on the disks and any single disk will not have all the blocks of the logical volume.

during the BIOS boot, the BIOS must read the boot blocks and boot strap the OS. however, if the OS components are striped among the disks, the BIOS would need to understand the striping and read blocks from multiple drives. this is unlikely to be a feature in a mass produced consumer-level BIOS firmware. it's not impossible, however, and it's possible that eventually there will be RAID-capable BIOS offered as a standard motherboard feature. i expect that this will be contingent on the success of SNIA's common RAID layout standard project that is being spearheaded by DELL and ADPT (at the moment their success seems highly unlikely).

that's where the RAID controllers come in. they do RAID logic in their own specialized firmware and present an integral device to the BIOS, so the BIOS can boot the OS without knowing that it's talking to a striped construct.