Raid 0 - Anyone Experience?

[Beggar]

I want to build a new computer. The new MBO provides RAID and it sounds interesting at the first glance to use it. I am thinking about RAID 0 with 2x750 GB disks. But the more I studied on the internet (there is a lot of guessing there and not always real information) the more insecure I got if it makes sense to use it. There are some disadvantages and not only benefits - apart from the big benefits for the industry ;-)

I would be interested if anybody uses it and the experience with it. Please let me know.

[Spoonman]

I had contemplated setting up a raid (6x1tb HDDS), however the cons seem to far outweigh the pro's and as such im running all 6 as JBOD.

[GingerLing]

Hi Beggar, I have RAID 1 (mirrored drives) on my home PC, just in case one drive fails everything is safely on the other and the system continues to work. There is not much point of using RAID 0 (stripping) as the performance benefit on home application use will not be realised. We use RAID 10 for our web servers (I work for a web software company), where large scale applications benefit from accessing information across multiple drives more quickly.

Below is info from Wikipedia, sorry I can't post a URL, not allowed.

There are various combinations of these approaches giving different trade-offs of protection against data loss, capacity, and speed. RAID levels 0, 1, and 5 are the most commonly found, and cover most requirements.

RAID 0 (striped disks) distributes data across several disks in a way that gives improved speed at any given instant. If one disk fails, however, all of the data on the array will be lost, as there is neither parity nor mirroring. In this regard, RAID 0 is somewhat of a misnomer, in that RAID is 0 is non-redundant. A RAID 0 array requires a minimum of two drives.

RAID 1 mirrors the contents of the disks, making a form of 1:1 ratio realtime backup. The contents of each disk in the array are identical to that of every other disk in the array. A RAID 1 array requires a minimum of two drives.

RAID 4 (striped disks with dedicated parity) combines three or more disks in a way that protects data against loss of any one disk. The storage capacity of the array is reduced by one disk. A RAID 3 array requires a minimum of three drives; Two to hold striped data, and a third drive to hold parity data.

RAID 5 (striped disks with distributed parity) combines three or more disks in a way that protects data against the loss of any one disk. The storage capacity of the array is a function of the number of drives minus the space needed to store parity.

RAID 6 (striped disks with dual parity) combines four or more disks in a way that protects data against loss of any two disks.

RAID 10 (or 1+0) is a mirrored data set (RAID 1) which is then striped (RAID 0), hence the "1+0" name. A RAID 10 array requires a minimum of two drives, but is more commonly implemented with 4 drives to take advantage of speed benefits.

RAID 01 (or 0+1) is a striped data set (RAID 0) which is then mirrored. (RAID 1). A RAID 01 array requires a minimum of four drives; Two to hold the striped data, plus another two required to mirror the pair.

Edited September 28, 2009 by GingerLing

[thaimite]

Just to emphasise the above.

Stay away from RAID 0 as your reliability is halved because EITHER disk failing will lose all your data

If you are after reliability and performance then Raid 5 is good but there is a very long rebuild and repair process should a disk fail, Thus for home use I would recommend RAID 1 or RAID 10 with 4 disks

Be warned though that RAID will not protect you against viruses because the mirroring will be copied to both disks before you know you have a problem.

I Do not use RAID, but have external USB drives that have full automatic backups using something like SyncbackSE for Data each night and disk imaging for programs (Drive C) with Acronis every week.

[Crushdepth]

RAID0 is ok *if* you backup your system regularly onto a separate physical disk. If you aren't inclined to make regular backups, stay away from it. If you do decide to go RAID0, its better to use smaller capacity disks. The higher the storage capacity the higher the density of the information on the disk and the more flaky they are.

[Beggar]

I had contemplated setting up a raid (6x1tb HDDS), however the cons seem to far outweigh the pro's and as such im running all 6 as JBOD.

What were the problems?

[Spoonman]

I had contemplated setting up a raid (6x1tb HDDS), however the cons seem to far outweigh the pro's and as such im running all 6 as JBOD.

What were the problems?

my motherboard only supports raid 0 and raid 1 and raid 0 is not an option i would ever chose, if it did support other raids and i chose say a raid 5 array if the Mobo died it would have to be replaced with an identical board (so im told).

That leaves two options, either a software raid or purchase an expensive raid controller card, neither option was i keen on and as im not really storing "irreplacable" data i just chose a JBOD set-up.

Edited September 29, 2009 by Spoonman

[Beggar]

Stay away from RAID 0 as your reliability is halved because EITHER disk failing will lose all your data

Be warned though that RAID will not protect you against viruses because the mirroring will be copied to both disks before you know you have a problem.

I often read on the internet that the reliability is halved if you use 2 disks to make Raid 0 . But is this calculation correct? Each disk should/could reach the MTBF. Even a concept with only 1 disk could break down after a week if the disk is faulty and a concept with 2 disks could run far beyond the MTBF. But I do not trust my disks anyway. On the other hand I had never a bad experience in decades. Sure - sometimes I had to hit a disk on the side to free a fixed arm...but they all still work, just get too small :-)))

Raid 1 I will avoid. As you say it does not protect against a virus so it is not a real backup. Because of this I always have an external backup. In my case I will have an external 1.5 TB drive to backup the 2 x 750 GB internal drives.

[Crushdepth]

If you have a two-disk RAID0 and one breaks, the RAID is destroyed. You lose your data because half of it was on the broken disk and RAID0 does not provide any redundancy at all.

RAID1 is a far safer and more useful option. It *does* protect you against the destruction of a single disk because an independent copy of your data sits on both drives. If one disk dies, you replace it and the surviving disk will copy the data back onto the new one. No flavour of RAID provides an independent backup.

[Beggar]

I see nobody wants to use or uses RAID 0. The problem with data loss does not count for me since I always back up my disks on not RAID drives. Data loss can occur with 1 or 2 disks and it can happen any moment.

But what I do not like so much is that the OS loses the control over the disk since it does not see it correctly - it just sees what the RAID controller reports. The RAID controller shows it to the OS as 1 single disk. Here you get some problems. Many tools that want to access the disk directly will fail. So it will be very hard to find tools that report S.M.A.R.T. data for the disks for instance (not even the temperature can be reported). But this is not so important to me.

The other problem what makes me think is that I could not find a tool that defrags a RAID disk. All the tools I found can defrag on the OS level but not really on the disk. So after a while the defragmentation might be severe - not on the logical OS level but on the physical disk level controlled by the RAID controller. And then arises the question if the access time to many stripes that are not in a perfect order is higher then the access time to a conventional disk that can be defragged physically. And there is a point where the higher access time because of fragmentation of the stripes makes the advantage of parallel read/writes to a disadvantage.

Perhaps I see this wrong. I could not find out how the Intel Matrix Storage Technologies works in detail on the stripe level to avoid this - I want to use this for RAID. Any ideas?

[surface]

Stay away from RAID 0 as your reliability is halved because EITHER disk failing will lose all your data

Be warned though that RAID will not protect you against viruses because the mirroring will be copied to both disks before you know you have a problem.

I often read on the internet that the reliability is halved if you use 2 disks to make Raid 0 . But is this calculation correct? Each disk should/could reach the MTBF. Even a concept with only 1 disk could break down after a week if the disk is faulty and a concept with 2 disks could run far beyond the MTBF. But I do not trust my disks anyway. On the other hand I had never a bad experience in decades. Sure - sometimes I had to hit a disk on the side to free a fixed arm...but they all still work, just get too small :-)))

Raid 1 I will avoid. As you say it does not protect against a virus so it is not a real backup. Because of this I always have an external backup. In my case I will have an external 1.5 TB drive to backup the 2 x 750 GB internal drives.

MTBF is only useful for large deployments. In such a case, you can calculate how often drives should fail based on the number of drives in use. A MTBF of 1,000,000 hours would mean that with 1,000 drives in use, you should expect a drive failure every 1,000 hours. It does not mean that all 1,000 drives will suddenly start to die around 1,000,000 hours (114 years) of use.

With regards to RAID 0, you'd be better off purchasing a new Intel SSD. RAID 0 is useful for scratch disks on workstations that deal with very large data set, such as video editing. Think 5 - 10 1TB disks in RAID 0. The performance of an Intel SSD is many times better for desktop usage than a RAID 0 array of standard 7,200 RPM drives.

[surface]

But what I do not like so much is that the OS loses the control over the disk since it does not see it correctly - it just sees what the RAID controller reports. The RAID controller shows it to the OS as 1 single disk. Here you get some problems. Many tools that want to access the disk directly will fail. So it will be very hard to find tools that report S.M.A.R.T. data for the disks for instance (not even the temperature can be reported). But this is not so important to me.

Any decent RAID controller, even those integrated onto desktop computer motherboards, should come with software that lets you view the SMART info from within the OS, and often within the controller's BIOS.

The other problem what makes me think is that I could not find a tool that defrags a RAID disk. All the tools I found can defrag on the OS level but not really on the disk. So after a while the defragmentation might be severe - not on the logical OS level but on the physical disk level controlled by the RAID controller. And then arises the question if the access time to many stripes that are not in a perfect order is higher then the access time to a conventional disk that can be defragged physically. And there is a point where the higher access time because of fragmentation of the stripes makes the advantage of parallel read/writes to a disadvantage.

I've never had a problem defragging a volume on a RAID array. This is pretty typical for file servers which are most likely to need it.

Perhaps I see this wrong. I could not find out how the Intel Matrix Storage Technologies works in detail on the stripe level to avoid this - I want to use this for RAID. Any ideas?

With Intel Matrix you can view the SMART info.

One thing that hasn't be mentioned, and which I have found to be the case with many years of use, is that standard IDE/SATA drives do not fair well under heavy use in a RAID array. For a desktop with typical use it may not be much of an issue, but these drives are certainly not designed to be as durable as their enterprise SATA or SAS couterparts.

Edited September 29, 2009 by surface

[Nagatus]

Just keep in mind that if you are not using a real RAID controller you will suffer a performance penalty.

The onboard (BIOS) controllers are so called fake raid, they really suck. They are even worse than software RAID 0

[Spoonman]

I see nobody wants to use or uses RAID 0. The problem with data loss does not count for me since I always back up my disks on not RAID drives. Data loss can occur with 1 or 2 disks and it can happen any moment.

If your seriously considering Raid0 you would be better of with JBOD, atleast when it takes a dump you only lose half your shit.

[Beggar]

With regards to RAID 0, you'd be better off purchasing a new Intel SSD. RAID 0 is useful for scratch disks on workstations that deal with very large data set, such as video editing. Think 5 - 10 1TB disks in RAID 0. The performance of an Intel SSD is many times better for desktop usage than a RAID 0 array of standard 7,200 RPM drives.

Video editing is exactly and perhaps the only reason for me to go to RAID. Firefox might not start much faster with it and is not worth the effort.

SSDs are simply too small, too expensive and too slow. Perhaps in 5 years. No noise, no risk of head crashs, perfect access times - future please come :-))

[Beggar]

I've never had a problem defragging a volume on a RAID array. This is pretty typical for file servers which are most likely to need it.

With Intel Matrix you can view the SMART info.

What software do you use for the defragmentation? I mean the physical defragmentation and not the logical in the OS - what all defragmentation tools can do. But they end at the RAID controller. I could not find one for the physical so far that tells the RAID controller where to position the data.

Intel Matrix reports to my knowledge a S.M.A.R.T. problem if required. Software showing the S.M.A.R.T. DATA I could not find so far. What do you use for it?

[JetsetBkk]

<snip>

I Do not use RAID, but have external USB drives that have full automatic backups using something like SyncbackSE for Data each night and disk imaging for programs (Drive C) with Acronis every week.

Similar for me - I have a 1.5 TB working disk and a 1.0 TB backup disk. The latter is a backup (synchronisation) of the important stuff from the working disk. The backups are done manually, regularly, and I review what has changed when I do the backup.

The problem as I see it with RAID is, as soon as you delete something or screw up your working disk, you immediately do the same thing to your other disk(s).

I also use Acronis every week to make an image of the C: drive.