NASLite Network Attached Storage

I am looking at migrating a bunch of disks from low end Compaq 300Mhz boxes to a bigger more modern machine.

I found a shop on ebay that sells unknown brand :

PCI IDE CONTROLLER CARD UDMA133 PC + RAID FUNCTION

assuming these work they are cheap enough for me to buy a few and have some spares (always a concern with RAID i am lead to believe)

Anyhow. The data i am migrating is just multimedia stuff and whilst it would be a pain in the ass to lose the cost of RAID x for the amount fo data (about 3TB) outweighs the cost of loss.

So i am thinking JBOD.

This card whilst an unknown brand seems from the picture like a decent buit of kit and has a good spec. So assuming it all works rather than just have 12 mount points im thinking JBOD might be better.

Does anyone know how reliable JBOD is.

Specifically if a drive fails are the other disks still ok?
Is their anything stored on 1 disk thats required for the JBOD array to work (i.e. if one disk fails are the other disks still ok?)

Can disks in a JBOS array be mounted individually if needed?
Is the implementation of JBOD very vendor specific i.e. this array works only with the exact card its made with.

Any other advice or flaws in my thinking?

Kudos

thanks for the reply. Coincidently i had read this exact page before.

For ease let me quote a relvant seciton



This brings me back to the original question...

in the specific context of NASLITE how does loss of a single disk and JBOD apply?

I think that for the purpose of combining disks in an array of any type, the hardware RAID solution is the best in terms of reliability. Any software solution that uses the main CPU for array management will be troublesome on some level.

A 3ware hardware RAID card can be purchased on ebay for a mere $70 or even less. Reinventing the wheel will often cost more and provide less in terms of value. If the data is worth keeping, then there is no substitute for a piece of hardware engineered for the purpose.

I know that I'm not answering your JBOD question directly, but I do think that the above applies. That is especially true for a machine that sits in the corner and get's no attention.

NASLite is built around the notion that user data is king. Anything that the OS does in terms of support or management is built to observe that. Introducing software managed storage disk arrays of any kind will be a regression.

Tony thanks for the reply.

The card i am referring to is very definately a hardware RAID card:

# Support two IDE channels with 4 P-ATA hard disks (note : No ATAPI devices support )
# Support RAID 0, 1, 0+1 and JBOD
...
# Maximum IDE data transfer rate up to 133Mbyte / Second
# Support over 137GB Big drive with LBA addressing
# Include one embedded CPU to handle the RAID function for reducing system loading and improving the system's ability

I am the first to admit the 3ware would be better however there are a few factors.

a 70$ 3ware card would be 2nd hand and very hard to replace with an identical one.

with regards to RAID:

RAID0 - one disk fails i lose all 4. I am not looking for speed so RAID0 is not an option
RAID1 - would be to much of a loss of HD space (i.e. 50%)
RAID5 - 3 pairs of 4 differntly sized disks means 3 RAID 5 arrays resulting in 750GB loss of data storage capcity in 3TB.

Hence why i was looking at JBOD. In theory i could have the same or slightly less MTBF as the seperate disks but with far fewer logical drives.


Another factor to take into account is that 3ware cards on eBay are predominently US based and for peeps in the UK there is a large postage and time premium.

Also migrating 3TB of data to RAIDx means a massive amount of data moving which may be able to be avoided with JBOD.

After many hours googling it seems that even with JBOD depending on the way the drive is partitioned the MFT would be on one physical drive. This is not very clearly explained but at this point i think this is a large single point of failure.

Let me look at this another way.

I am looking to have many drives but with few mount mounts. Can this been done in V2 with NFS now.?

Your suspicions are well founded.

As I understand it, JBOD means the concatenation of the space of all disks to present one logical disk volume to the operating system. As such, if one disk fails, the operating system will see that as a prolem for the whole disk from its perspective. This means that you lose everything much like RAID 0.

You may be able to recover the files on the surviving disks but only through special utilities that let you view the disk structure and decide where the file starts and where it ends. Not a task I would want to go through....

Having just experienced the failure of a brand new disk, albeit with only 100 or GB of files on it, I just bought an adaptec 2400A card to use for RAID5.

thanks for the reply.

i am beginning to think it would be better to scrap all my drives (aka sell them) and repalce them all with SATA ones in RAID 5 with 3ware.

Without meaning to go to off topic can anyone comment on the re-dimensioning of a RAID 5 array with 3ware.

e.g. Day1 = 3*400GB drives in RAID5
Day 2 = add a 4th 400GB drive.

is this simple and reliable and fast. I am concerened that once it get to 10 disks it will take days to rebuild the array after adding a new drive.

Something else to be wary of ...

When you have two IDE channels with four disks, these are configured in master/slave pairs - a failed slave will typically hang the system momentarily whilst a failed master will typically cause a system lockup requiring a reboot (common in cases where a swap file is on the failed disk)

Either of these conditions can cause a problem with a RAID array, which may sense the condition as failure of a second disk with subsequent loss of data.

Better hardware RAID cards will have four separate channels each intended to support a single drive configured as master.

excellent tip fordem

At this point i am seriously considering just having lots of un raided disks again.

RAID has to many variables at this time vs a high cost.

It's your data, it's your money, it's your choice.

Whilst RAID should not be seen as an alternative to backup, it does provide protection against disk failure and having worked with RAID for many years now, I consider it mandatory on any "storage" server.

Over the years SCSI RAID has worked very well for me, but my albiet limited experience with PATA RAID has not been good, and so far SATA RAID has functioned satisfactorily.

fat,

Another thing to consider is not just HD failure, but the raid card failing. and trying to rebuild the array.

Whilst it does happen, in over 10 years, and more disk failures than I can recall, I have had only one RAID controller fail.

In fact, I have seen more server motherboard failures than I have RAID controller failures, so I would be more concerned about motherboards with integrated RAID than I would be about expansion cards.

A raid card failing is definately a concern.

Eventually i want to replace all my disks with one large say 12*500GB RAID 5 array.

At this size the RAID card is economically viable however not so much that i can have a spare at hand just incase.

Should it fail i would need another quickly (as 5.5TB of data is obviously important regardless of what it is) however to get a replacement quickly i would have to use the commercial route (i.e. not an eBay deal).

Currently i would be looking at about £500-600 UKP to replace a 3ware card quicky and thats a significant amount of money.

Then their is the whole question of perhaps having to replace like for like in order to use the array

i.e. replace a 95xx with another 95xx and not a 95xy

In some respects based on current prixing i can purchase about 1.2TB of HD space (4*300GB) for about £200 UKP. This is cheaper than a 8 or 12 port ebay 3ware card and rsync could be used to have some sort of incremental backup. Not perpect but it does give me time to really get into RAID and look for deals.

Dont get me wrong i have been using RAID cards for years and i agree in that time i have had about 3 disks fail, 1M/B and 1 RAID card. These were high end Dell type affairs and so a failure was just a matter of ringing up and claiming against warrenty but when its my home i dont have that luxury and have to really consider the options.

Lastly, we also have to consider the rate at which HD size increases and costs come down. Its not that long ago a spend as much on a 17GB drive as i could get a 750GB drive now. So speding a fortune on HD capcity i wont use for a year will certainly be a false economy.

Just FYI and context - i converyt all my multimedia (e.g. DVD and CDs) into avi and mp3 and use XBMC thoughout my home to play them. So data sizes are huge but content wont be lost should a failure occur however replacement time would be very long.

Hi Fat,

The card failing is a concern, more so then the HD's after all thats what raid is for, there are plenty of cards on ebay but the problem is if the card dies you could loose your data. and "some" people have lost more data using raid then if they hadnt. user error etc.

i guess its a case of how much is your data worth to you? I know mine to me is worth a lot i.e. kids photos, DV video of parties etc mp3's avi's etc.

looking at the price of decent Raid cards one would be nice but to buy two of them. I do like single drives one packs up and it does not impact on the others i.e. data loss. a few years back you could get a handful of DVDR's and back up most of your data but now with the size of HD's and the price its not viable to back up entire HD's to DVDR only bits you consider important.
for the price of two decent cards you could build another NAS with TB's of storage and have money left over.

Here is a link for the 3ware cards the company is UK based.
http://www.span.com/catalog/index.php?cPath=24