Computer Questions

[Taz]

Any computer guru out there can give the advantage in going with raid set up instead of two hard drives and back up software and what is the difference between raid 0 and raid 1

 

[David Prall]

Raid

Hi Taz,

Raid 0 is used for performance/speed and is also known as striping. It doesn't provide data backup, but writes the data to both drives simultaneously to increase performance.

Raid 1 creates a mirror of your primary hard drive on to the second, providing a complete and always up to date back up of your primary drives data. (It does it on the fly without any intervention on your part)

While you can certainly use tape back ups, etc to protect your data, it is only able to restore all data saved on your drives up to the time the back up is made. Any data added to the drives between back up times would be lost, while Raid 1 is always up to date.

I hope that helps.

 

[Tiberium]

Unless you are running a server you do not need to run a raid setup and now with SATA320 the performance gap is almost closed.

 

[amey01]

Any computer guru out there can give the advantage in going with raid set up instead of two hard drives and back up software and what is the difference between raid 0 and raid 1

Two hard drives and making a backup is similar, however with RAID 1, the backup is automatic - it is managed by the server / RAID controller. The other advantage of RAID is redundancy - that is, if one of the disks fails the other will take over automatically and everything will be seamless.........then it is simply a matter of hot-swapping the failed drive and the new one will automatically rebuild itself. Of course, all of this is dependant on what sort of RAID controller you use and what sort of SCSI system is in use. I am speaking from experience on high-end business servers, however the home stuff might be a little different.

 

[Peter Hogan]

Hi Taz,

While you can certainly use tape back ups, etc to protect your data, it is only able to restore all data saved on your drives up to the time the back up is made. Any data added to the drives between back up times would be lost, while Raid 1 is always up to date.

I hope that helps.

Hi,
This can also work to your disadvantage. If something happens to the computer (a virus, for instance) that causes data on the disks to become corrupt, you'll be trashing BOTH copies simultaneously (been there, done that). With a tape backup, you have a 'clean' copy to restore from, albeit minus the data since the last backup. If you do daily incremental backups, and a weekly image backup, you would only lose a maximum of 1 days work.

RAID 0 gives you a bit more speed, but LESS security than a single disk, since if either disk fails, you lose ALL the data on both disks.
RAID 1 gives you more security than a single disk, since the data is mirrored on the second drive. However, you only get 50% of the total storage capacity of both drives, i.e. two 250 GB drives total 500GB capacity, but you only get 250GB useable.
RAID 5 distributes data and error checking data amongst multiple drives, allowing all data to be recovered if any single disk fails, similar to RAID 1. However, the total capacity is the sum of all the disks less one, i.e. if you have 5 250GB disks in the array, the total capacity is equal to 5 minus 1 = 4 disks, or 1000GB. This give a much higher useable vs total capacity than RAID 1, in this case 80% vs 50%. As with RAID 1, in RAID 5 if a disk fails, you can swap it out, rebuild the array, and lose no data.

Before I used RAID 5, I had a disk fail and had to re-rip several hundred CD's to the new disk (NOT fun), now I can recover from a disk failure simply by swapping out the bad disk. The investment in disks is not insubstantial, but it IS worth it for security reasons, and if you compare it to what you spend on other parts of your audio system, it's not out of line...

If you have multiple copies of your music library on different computers (a second copy on an external drive at work, for instance), I have found this free program good for keeping them in syncronization (i.e. all songs the same on both systems). Not involved with them in any way, it simply works well (for non-music data also).

http://allwaysync.com/

HTH,
Peter

 

[David Prall]

Expanding on Peter's advice, if the 5 disk array is more than you intended to spend, AND you are actually only going to use this system for music archival, the limitation of only having data as current as your last back up would not really be a big issue, since you could initiate a back up any time should you do a lot of new music loading. Conversely, if you go with the disk array, your disks are always up to date with your latest music load, so there is no system downtime/slowdown for a back up utility to run.

 

[Taz]

Thanks for the feedback, the peformance gain from raid 0 is in a great deal?

 

[David Prall]

Theoretically I suppose it should be twice as fast, since it writes to both disks simultaneously. But it doesn't really work out quite that way in practice. One the practical side though, unless you're a gamer, or going to have the disk accessed by multiple concurrent connections, it's probably just overkill, and you would be better served by implementing some sort of back up scheme if your music collection is large. But that's just my opinion, and it is possible that some of the others here may have opinions that differ.

 

[SteveInNC]

Thanks for the feedback, the peformance gain from raid 0 is in a great deal?

To clarify what David said, striping writes different pieces of a file to different disks, so both disks in the set have to be functional, or have additional redundant copies to be able to read your data back.

The performance gain is not significant for normal consumer purposes, IMHO . The rest of your system has to have the bandwidth to take advantage of the striping, and it's mainly useful for high-demand data like video editting, enterprise databases, etc. In those cases, the preferred interface is SCSI instead of ATA, although eSATA is starting to get there. Add to this that many consumer-grade RAIDs are implemented via software on your computer, and you have another potential bottleneck if you are looking mainly for a performance boost.

Ideally, each disk in the array is also running on its own drive controller.

Striping was particularly useful back when drives had minimal to no on-board buffering of data, and the drive platters and head seeks were significantly slower than those of modern drives. There is a whole bunch of CompSci theory around how best to organize data on a disk to minimize latency, head seeks, and other stuff. In the old days, having more "spindles", aka drive mechanisms, tended to improve those efficiencies.


FWIW, you can also run RAID 0+1, 10, or 50, which gives you striping and redundancy, but uses even more drive mechanisms. (They all have slightly different performance and redundancy characteristics).

RAID=Redundant Array of Inexpensive Disks

Here's a link to the original Berkeley paper from 1987 describing the concept of RAIDs:
http://digitalassets.lib.berkeley.edu/techreports/ucb/text/CSD-87-391.pdf

As mentioned previously, RAID is NOT a backup. It supplies redundancy for certain types of hardware failures. If you get hacked, or accidentally nuke your data, it's gone. RAID is particularly useful for people that can't afford downtime due to a hardware failure, even just the time it takes to reload a backup.

Offline backups are the only true form of backup, whether that's a simple snapshot of a disk image to another drive, a formal incremental file backup, or spooling off to tape or other media. To be really safe, you should occassionally reload one of your offline backups to an active volume to insure 1) that it actually got writtten out properly the first time *, and 2) that the backup media is still intact.

* I know of one company that had a really consistent backup plan, with weekly full backups, and nightly incremental backups. Unfortunately, they discovered the hard way that they were writing only the directories of their files to the backup volumes, and were not including the files themselves... A cursory look at the backup log would show that a whole series of directories had been traversed, so at first glance, everything appeared correct...

 

[David Prall]

Thanks for the assist Steve! Yours was the most complete and informative post yet.

 

[Jeff Zaret]

Just my 2 cents and to agree with everything which has been posted here. I am a network administrator and one of the many duties is disaster recovery which
includes backups.

Raid is a great idea but not really practical for home use. IMHO, it is more of a peace of mind for home. I would recommend either backup to tape or better yet since disks are cheap and one can build a system fairly cheap now, to do the backup. You could create/build a "bare bones system" which does nothing but backup. Buy a large disk or two and have nightly (incremental) and/or weekly full backups of your stuff. Depending on how often you data changes will tell you how often to create a backup and what type.

Just a thought

Jeff

 

[Taz]

Thanks for all the replys good info, has you can tell I am looking to upgrade my pc and trying to figure the best way to go, even looking at macs but I have never had one and I am worried about compatability there site says it is not a issue anymore but I don not know the also claim to be faster and safer any thoughts?

 

[Tiberium]

http://www.westerndigital.com/en/products/Products.asp?DriveID=190

Buy the new raptor drives they are by far the fastest on the market.

http://www.tomshardware.com/2006/02/06/wd1500ad_raptor_xtends_performance_lead/

Here is a review.

 

[Audiophiliac]

When I built my first PC a couple years back, I thought I would be cool and run a RAID 0 to store my music on. Worked fine until the controller went south and took both drives with it. Fortunately I also built a 400GB USB drive to use as a back up and had just finished backing up less than a week before the failure.

WD replaced the drives under warranty, but the RAID controller on the motherboard is toast...as is the floppy controller...other than that, the PC still operates nicely...I use it as a foot rest now.

My new machine just has a single 400GB drive for storage (120 system drive). And I back that up to the USB drive as well as archive my music to DVD-R. But the 400 is almost full now....so I am debating either buying another couple of drives and doind a RAID again (RAID 5 most likely), or just buying a new 750GB single drive.