After seeing unRAID featured on last weeks systm show (http://revision3.com/systm) I thought this would be ideal use for my spare desktop & limited drive space on my Laptop.

 

I've set it up ok (with help from the lime-tech wiki manual) and now have a system comprising:

 

parity device: 500Gb Western Digital

disk1 device:  500Gb Maxtor

disk2 device:  500Gb Maxtor

 

I've created a sinlge share called NAS

 

When I map "\\tower\nas" it appears on My Computer under Network Locations (running Vista SP2) as expected, but is shown as 931Gb drive. Is this correct?

 

I expected to only see around 465Gb as both the Maxtor drives would be mirrored???

 

Thanks for any insight

 

Cheers Nez

After seeing unRAID featured on last weeks systm show (http://revision3.com/systm) I thought this would be ideal use for my spare desktop & limited drive space on my Laptop.

 

I've set it up ok (with help from the lime-tech wiki manual) and now have a system comprising:

 

parity device: 500Gb Western Digital

disk1 device:  500Gb Maxtor

disk2 device:  500Gb Maxtor

 

I've created a sinlge share called NAS

 

When I map "\\tower\nas" it appears on My Computer under Network Locations (running Vista SP2) as expected, but is shown as 931Gb drive. Is this correct?

 

I expected to only see around 465Gb as both the Maxtor drives would be mirrored???

 

Thanks for any insight

 

Cheers Nez

 

The Maxtor Drives are not mirrored.  The share you created "NAS" spans both of the Maxtor drives.  You get the protection from a drive failure (one of the Maxtors) from the parity drive (the WD)

Ahh....i think i get it........it's not really a "RAID" but acts like one? (hence the name unRAID perhaps?)

 

So I've actually got nearly 1Tb of storage available spanned across the two disks & if either one fails, the parity drive can "rebuild" the lost data onto a replacement drive.

 

Apart from checking the GUI occasionally, how do I know I've lost a drive, will it be through the apparant reduced size of my share? What if the parity drive were to fail, how would I know that?

 

 

Cheer, Nez

Apart from checking the GUI occasionally, how do I know I've lost a drive, will it be through the apparant reduced size of my share? What if the parity drive were to fail, how would I know that?

Check out unraid_notify.

Ahh....i think i get it........it's not really a "RAID" but acts like one? (hence the name unRAID perhaps?)

No, it really is RAID... but not one of the normal raid numbers you are familiar with.  It is RAID4, but without striping of data across drives.

When RAID4 was originally "defined" as a standard, disk drives were much slower... The striping was a method to get faster performance from slower drives since multiple requests for consecutive sectors could be issued to multiple drives, and each seek to the sector in parallel.

 

Today's drives are easily able to keep up with media server needs, without resorting to striping, so by eliminating striping, but keeping the rest of RAID-4 (the single dedicated parity drive for a number of data disks) unRAID can offer a major feature, the ability to mix and match different sized data drives and to grow incrementally with ease..

 

So, you really do have RAID, with a single parity disk, and even it can be upgraded as drive sizes grow, so you are not limited by it as 2TB drives and bigger become commonplace.

 

One fact about your two drives seen by windows as one total sized volume.... a single file cannot span two disks... You cannot create a single 600Gig file if all you have is two 500Gig drives... even if you have a total of 900Gig free.

So I've actually got nearly 1Tb of storage available spanned across the two disks & if either one fails, the parity drive can "rebuild" the lost data onto a replacement drive.

exactly correct.

Apart from checking the GUI occasionally, how do I know I've lost a drive, will it be through the apparant reduced size of my share?

No, in fact, the data disk would be simulated by the parity and other data disks.  You could still read and write to the failed drive.  Unless you looked at the management interface, you would not know a drive failed at all.  Odds are high, with normal use, you would never see the loss of performance (because all the disks need to be accessed to recreate the failed disk, it is not able to be read as fast.)

 

Now, the loss of performance is not that high in many cases, especially if you only have a few drives and the PCI bus can keep up (it, on older motherboards, is the eventual speed limiting bottleneck, not the disks)  On my old IDE based Intel MB, I was able to simulate a failed drive (by un-assigning it) and starting the array.  I was still able to serve up 4 different ISO images from the failed drive, to 4 different client PC's/Media players on my LAN, and all played perfectly.

What if the parity drive were to fail, how would I know that?

As currently delivered by lime-technology, you need to keep watch on the management web-page.  Any drive with a "red" indicator has failed.  A single drive failure will not stop the array. (A huge feature)

 

Many of us have added e-mail notifications, or LAN based notification of drive status.  Look in the Customizations sub-forum for those threads...

Look for unraid_notify.sh

 

You can simulate a failed drive by stopping the array, and either un-plugging a drive, or un-assigning a drive.

Beware of the button labeled as "Restore"  It DOES NOT restore data.  It restores an initial configuration based on the currently assigned and working disks and throws away parity.  If you were to press it when a failed drive is present, you will throw away the ability to recreate that drives data from parity. 

 

For any FAILED drive, (or a drive you are upgrading in size) you would use the "Start" button to start the array after replacing the failed drive.  (sometimes you need to check the checkbox under the start button to enable it)

 

Have fun with your server...

 

Joe L.

Oh yes, use the latest 4.5beta6 beta.... It has a fair number of fixes over the 4.4.2 and only one known issue (you can't add more than 16 drives, even though it is supposed to be able to now handle 20 disks...).    The array can apparently handle more than 16, but the management console can't, and is unable to mount the 17th disk.  I'm sure that will be fixed in the next version, and it affects very few people, as most do not have a full array.

 

You can upgrade by downloading and un-zipping the newer release and dragging the bzroot and bzimage files from it to the flash drive and then re-booting.  No need to re-configure or re-format the drive, or reload syslinux, as those are usually one-time tasks.

 

Joe L.

Thanks for the very quick and detailed replies!

 

Yes, I hope to have fun with my 1st ever server!!!

 

Cheers, Nez