Raid 5

MouthBoy

MouthBoy

MouthBoy

Soldato
Joined
6 Apr 2010
Posts
2,919
Location
Cambridgeshire
I have had some concern lately with loosing my data on my PC. I have always kept a clean system but that doesnt mean that my HDD wont suddenly die on me. I am not bothered about my games or my windows install, and they are recoverable quickly but I am concerned about my personal data and my uni work.

Currently I have a 500gb F3 for boot and games. I have a 1Tb drive for my data, and that is backed up (when I remember to manually backup) to 2 x 1Tb WD Mybooks. However, I want to setup a method where I wont have to worry "I havent backed up in the last 30minutes".

Would replacing my current 1Tb drive with 3 1Tb F3s in Raid5 be a solution? If I correct, I would have 2Tb of storage with a 1Tb parity just in case of a drive failure. This would suit me but is it worth it? I would be using my onboard raid controller to do this too, so will that cause issues? I am not a major business here so I am not willing to shed out cash on a raid card and things, but I can afford a few drives to work with..

Thoughts?
 
You might find it easier to do a raid1, as (as far as I know), Windows' support for Software RAID-5 is rather pants.

If you've a linux box, just head to a prompt and type man mdadm and get cracking ;)
 
Actually though, in general yes that's a similar set up to what I have. I've a linux server with software raid-5, and I'll back that up to externals when I get the chance. I haven't had any drive failures yet, but it's quite a nice way of working I believe. So your philosophy is correct :)
 
Raid is not a backup.

Raid is for high availabilty, performance, and redundancy. All valid goals, but it still doesn't make it a backup solution.
 
whitecrook said:
Raid is not a backup.

Raid is for high availabilty, performance, and redundancy. All valid goals, but it still doesn't make it a backup solution.
Click to expand...

Sorry, I didnt explain very well. Its not going to be a "backup" as such. Its just "insurance" to know if I am working on something and something bad happens, I dont have to panic. I will still backup as much as I can to my externals.
 
blueacid said:
You might find it easier to do a raid1, as (as far as I know), Windows' support for Software RAID-5 is rather pants.

If you've a linux box, just head to a prompt and type man mdadm and get cracking ;)
Click to expand...

It would be hardware raid 5 on my motherboard, not windows raid 5.
 
Personally, (and I posted it before here) I think Raid, for most people, in the home is a total waste of time.

Why would you go for 3 1TB drives, rather than 2 2TB drives, still have the same capacity, but less drives required? How many users are you serving?

If you are working and your drive goes down, say, are you going to keep working or are you going to fix it? What is the difference between that and having a failed drive and then fixing it?

It is when rebuilding the array after replacing a disk, that the second disk is most likely to fail.

Also, when rebuilding/checking the array it's slow as heck and pracically unusable for hours while it rebuilds. Have you got a UPS on your computer? battery backed raid controller? If not, you should consider what the point is.

Basically it's more complexity, more to manage, for what ? Why don't you just run a rsync/cron job to do a delta change sync every minute.
 
whitecrook said:
Why would you go for 3 1TB drives, rather than 2 2TB drives, still have the same capacity, but less drives required? How many users are you serving?
Click to expand...

Well obviously the 3 drives as raid5 has a minimum requirement of 3 drives, 2 active and 1 parity.

whitecrook said:
Why don't you just run a rsync/cron job to do a delta change sync every minute.
Click to expand...

Explain more? I never heard of rsync? If thats to backup to my WD Drive every minute its not going to be a good solution. If I am working on huge files that can span gigs and gigs, to have to send that information via USB every minute would be slow and annoying.
 
smeaney said:
Well obviously the 3 drives as raid5 has a minimum requirement of 3 drives, 2 active and 1 parity.
Click to expand...
Raid 5 is striped parity, so it's actually a third of each disk. I think its Raid 4 that has a dedicated parity drive.

Explain more? I never heard of rsync? If thats to backup to my WD Drive every minute its not going to be a good solution. If I am working on huge files that can span gigs and gigs, to have to send that information via USB every minute would be slow and annoying.
Click to expand...

Rsync is just a very standard universal way to synchronise data (remotely, but it does local as well). It works by only copying the difference in a file, so even if your file is gigabytes, it will only copy the difference, which is usually much smaller. The more frequently you check the less data it has to copy.

In saying that though, you possibly might be better off with the 2 disk RAID1 mirror.

Generally for a 2 disk raid 1 or 3 disk raid5
RAID 1 - write = 1x, read = 2x
RAID5 - write=slower than 1x, read 2-3x, RAID 5 also has the benefit of more spindles, which can decreases latency especially if your array it being hit by multiple users.
RAID1 has benefit of being 'a whole' and you should in the event of disaster be able to still do something with either disk, but in the RAID5 setup retreiving data without rebuilding the array can be a problem. But then that's why you have backups.


Configure it and test it! remove a disk, does it still work etc? Add a blank disk in, does it rebuild?
And dont forget to setup monitoring. No good having an array if you don't know what state it is in.
 
So, with that said, it seems that a raid1 would be better for me. Maybe 2 x 1Tb drives? Do they have to match compleletly? Or can it be my current 1Tb with a newer 1Tb?
 
smeaney said:
So, with that said, it seems that a raid1 would be better for me. Maybe 2 x 1Tb drives? Do they have to match compleletly? Or can it be my current 1Tb with a newer 1Tb?
Click to expand...

If you use two different size drives, the smaller of the two will dictate the size. Any "wasted" bytes at the end of the larger drive are typically unavailable.
 
blueacid said:
If you use two different size drives, the smaller of the two will dictate the size. Any "wasted" bytes at the end of the larger drive are typically unavailable.
Click to expand...

Thats cool then, so if I ordered an F3 1Tb drive, I would be able to Raid1 it with my current 1Tb drive? If so I shall look into doing this.
 
You must log in or register to reply here.
Back
Top Bottom