Possibly OT... Hard Disk question

I'm not seannie but I can give you the Maths on RAID!

If you use RAID level 0 (concatonation) all your hard drives appear as one single HUGE hard drive but you get zer o fail over, if a single disk dies ALL your data is lost.

The "safest" RAID level is 1 (mirroring) but it is also the most wastefull. If you have two hard disks it basically duplicates one onto the other so you loose 50% capacity. If you had 4 disks and you wanted mirroring you'd combine RAID 0 and RAID 1 to give you RAID 0-1 i.e. concat the first two disks togther, the last two together and then mirror the first two on the last two. Again, very secure but very wastefull, 50% loss of space.

The most common RAID level is 5 (I have no idea what happened to 2,3 & 4). The idea behind RAID 5 is that you have n disks, n-1 are used for data and 1 is used for checksums. If any single disk dies the checksums are enough to re-construct the data and hence restore all your data. If 2 or more disks go you loose EVERYTHING. Hence the security is not as good as RAID 1 but it is more space efficient. If you have 2 disks in RAID 5 you have RAID 1 so no point. If you have 3 disks in RAID 5 you get 2/3 for data, hence 33% loss. If you have 4 disks it's 3 for data and 1 for checksums so you get only 25% loss, 5 disks 20% loss and so forth. Of course the more disks you are sticking into RAID 5 the more chance of lossing more than one disk at a time and hence loosing the lot!

The most common RAID 5 configuration is with 4 or 5 disks. That's all well and good for servers with large cases but not really realistic for your average home PC, hence you'll most probably end up having to go with RAID 1 and loosing 50% capacity in exchange for very resiliant storage.

As has been said already on this thread, Hard drives are NOT reliable, you can't count on them. Personally I just don't see backing up 200GB onto DVDs are practical (that's 50 DVDs), hence I bought TWO identical external disks that I'll be mirroring off each other. THat works out at 200GB of robust storage that I can be confident in for about 400 Euro. Yes, it's expensive, but my Data is bloody valuable to me so I see it as money well spent!

In the future I plan on buying a server with RAID 5 for the house but untill I get a serious pay rise my two external disks will have to do!

In the future I plan on buying a server with RAID 5 for the house but untill I get a serious pay rise my two external disks will have to do!

Or until I get back into Maxtor with a larger coat...

That's great Bart - thanks for the info - its very helpful.

Doing the research led me to controllers. The RAID 5 controllers are expensive. I could do RAID 0, 1 and 10 with the controller I have my eye on (it does another flavour of RAID, orsimilar, but I forget what it was - not a number anyhow). Its not a RAID 5 controller but will manage four disks. I guess I'll probably go for that and a couple of 300 gig disks for a total of about 340 quid. Just over one euro per gig, mirrored I can add a couple more later on (a tad over 100 quid each).

Funnily enough, I've had PC's for over 20 years now and never had a hard disk fail, My current disks are about 2 and 4 years old - no hint of a problem. Of course, I've lost data, but only due to operator error

I'd hate to lose a hard disk but I guess my livelihood doesn't depend on it - so your needs are definatley more critical.

Still, I'll mull the whole thing over - perhaps the external storage is the way to go. I'll keep researching

And thanks everyone for the advice and guidance - really appreciate it. Even better, its free!

Dave

The most common RAID level is 5 (I have no idea what happened to 2,3 & 4).

I'll spare you the history lesson...

RAID5 is dog slow, especially if we are talking 4 or 5 IDE disks. If you are just reading off it its probably ok for home use, but writing to it will be annoying. Not as annoying as a large USB disk but not far off. If you want to maximise your storage with some redundancy and dont care about performance then its the way to go. Its all about trade offs.

All my home data is now on ZFS Raid Z . Bart you might have it soon enough for Mac!

Cheers,
~Al

Doing the research led me to controllers. The RAID 5 controllers are expensive. I could do RAID 0, 1 and 10 with the controller I have my eye on (it does another flavour of RAID, orsimilar, but I forget what it was - not a number anyhow). Its not a RAID 5 controller but will manage four disks. I guess I'll probably go for that and a couple of 300 gig disks for a total of about 340 quid. Just over one euro per gig, mirrored I can add a couple more later on (a tad over 100 quid each).

If you can find a way to connect the disks to the machine then software raid might do you. I assumed Bart meanst software raid. I dont know how/if windows supports this freely. Sun's software raid manager is free with Solaris, I assume linux has something that works too. Not using windows might be out of the question on your workstation, but you could set up a unix machine as a file server and share that out to your windows machines. The network is the Computer

You can buy a brand new computer from Dell,sub 400 euros, with vastly superior HD storage cheaper than you can upgrade that stone age PC.
Also,You can buy a USB "dongle" from Maplin (which can fit on your key-ring) with MORE than 1Gb storage for around 40 Euros.

Folks - looking for some advice. I need to beef up my PC and am looking to get a couple of 250 GB hard disks to store all my images and catalogues

The PC is around 2001 vintage (HP Vectra) and has served me well. The processor and RAM is fine. I don't want to buy a new PC - just a couple of new hard disks. Trouble is, I'm not sure which ones I need.

The Computer Management console lists the two current hard disks as SCSI devices, but they're not. I'm fairly sure they are EIDE. The controller is an Intel 82801AA Ultra ATA. The two hard disks are IBM-DTLA-307030 and a WDC WD80-0BB-00CAA1.

On the web, I'm seeing IDE devices, EIDE devices, ATA100, ATA133, ATAII - you name it... So, if anyone can advise me on what I need, please let me know.

Thanks in advance and sorry if this is a little OT.

Dave

My interpretation of what you are seeking is capicity and security for important files. So its a storage issue, seperate from the computer issue.
To me then external storage seems to be a logical choice. I'm not a fan of usb storage devices but I am of NAS. This is a reliable long term solution that is independent of your computer. There are several price points suitable for the "home user" Iomega offer these www.iomega-europe.com/eu/en/products/nas...nh4IQCFQlwQgodbGUTnQ Higher up the scale are these from Buffalo www.buffalo-technology.com/products/storage.php .
These are all fairly good solutions - for a price - but if you are prepared to spend the money to retrofit a RAID system to a 2001 computer then you can afford a pretty good one of these devices.
I have lost entire systems that were on RAID, its a technology not a guarantee. Have a backup strategy - that's the key.

JMP