[BlizzardUK]

I plan on getting a P8Z77-V PRO any idea if this will be any good for 4x 3TB 7200rpm RAID 5 mode ? I have heard about things being slow on RAID 5 for motherboard controllers, but those articles could be outdated.

Also what sort of speed should I expected with RAID 5 via a motherboard ? I want at least 65mb a second if possible.

Any idea ? Thanks.

[c4rv]

There are couple of problems with motherboard RAID 5, firstly its software RAID so you CPU will be doing the XOR calculations and second if you motherboard dies you could have a real problem recovering the data. Performance wise, its a LOT better reading then writing, you didn't mention if you are concerned with read or write speed.

[Loobster]

RAID 5 was good when disks were ridiculously expensive, but not these days.

The last time I specced a server with RAID 5 was when I was in England, so 4 years ago or more.

If you want redundancy and speed, RAID 10 is the way to go.

[Esot-eric]

Don't bother with the motherboard RAID, the performance wont be noticably different to using pure software RAID (and as c4rv says if your motherboard dies you may have problems getting to your data).

Speed should be fine.

I'm running Debian Squeeze on a HP ProLiant Microserver (1.3GHz Athlon II Neo N36L) with 3GB RAM and 5x 1.5TB 5900RPM drives and get good performance with pure software RAID 5 (mdadm).

Write:

$ dd if=/dev/zero of=/mnt/raid/files/output.img bs=8k count=256k
262144+0 records in
262144+0 records out
2147483648 bytes (2.1 GB) copied, 19.6802 s, 109 MB/s

Read:

dd if=/mnt/raid/files/output.img of=/dev/zero bs=8k count=256k
262144+0 records in
262144+0 records out
2147483648 bytes (2.1 GB) copied, 6.68938 s, 321 MB/s

Over the gigabit network i get around 70MBps to 80MBps transfer speeds using Samba.

[c4rv]

Originally Posted by Loobster

RAID 5 was good when disks were ridiculously expensive, but not these days.

The last time I specced a server with RAID 5 was when I was in England, so 4 years ago or more.

If you want redundancy and speed, RAID 10 is the way to go.

RAID 5 definitely still has its place when you are talking about have 4 or more drives in a system. Don't forget that most servers these days have switched to 2.5" SAS drives which still have capacity limitations.

Even on a 4 disk system you are losing the size of one drive compared to RAID 10.

[flagpole]

Originally Posted by c4rv

There are couple of problems with motherboard RAID 5, firstly its software RAID so you CPU will be doing the XOR calculations and second if you motherboard dies you could have a real problem recovering the data. Performance wise, its a LOT better reading then writing, you didn't mention if you are concerned with read or write speed.

are we sure that the cpu will be doing the parity calculations? i thought motherboards had their own raid controllers these days?

[c4rv]

Originally Posted by flagpole

are we sure that the cpu will be doing the parity calculations? i thought motherboards had their own raid controllers these days?

Na, ICHR controllers from intel are software based.

Don't know about nvidia and AMD chipsets but the performance figures are not much better.

[Loobster]

Originally Posted by c4rv

RAID 5 definitely still has its place when you are talking about have 4 or more drives in a system. Don't forget that most servers these days have switched to 2.5" SAS drives which still have capacity limitations.

Even on a 4 disk system you are losing the size of one drive compared to RAID 10.

Your comment is correct, technically.

But when offered a RAID 5 system and a RAID 10 system to customers, I find without exception that the performance gains are well worth what is now only a little extra initial outlay.

RAID 5 does have 'its place', but only among the most frugal of customers who don't care about performance with today's resource hungry Server OSs.

[Loobster]

Originally Posted by c4rv

Na, ICHR controllers from intel are software based.

Don't know about nvidia and AMD chipsets but the performance figures are not much better.

It helps to specify what you mean by 'software' in this context, since the software you speak of is actually embedded firmware, not 'software' in the traditional sense, where the OS would be doing the calculations.

If the mobo offloads the hard work to the CPU, that's still technically hardware RAID - just not with a dedicated RAID controller with an on-board processor.

[c4rv]

Originally Posted by Loobster

Your comment is correct, technically.

But when offered a RAID 5 system and a RAID 10 system to customers, I find without exception that the performance gains are well worth what is now only a little extra initial outlay.

RAID 5 does have 'its place', but only among the most frugal of customers who don't care about performance with today's resource hungry Server OSs.

You realise that as well as expandability, hardware RAID 5 actually offers better performance then RAID 10 when you start adding more drives ?

[Loobster]

I can't think of any scenario where it would, even for reading, and certainly not for writing.

If you had 10 drives in a RAID 10, you'd be pulling data from all of them when reading, and have the writing speed of a stripe to 5 disks. With RAID 5 you still have massive calculations when writing, and you would only pull data from 9 disks when reading.

Perhaps you can give an example of why you imagine that RAID 5 would give better performance (in any scenario).

[Maxatoria]

raid's job isn't about performance but about maintaining the data in the event of a drive failure thereby keeping the uptime to as close to 100% as possible and with a dedicated card theres very little overhead in raid 5 since the card handles the hardwork (and you can move the array easy between machines)

[flagpole]

Originally Posted by Loobster

I can't think of any scenario where it would, even for reading, and certainly not for writing.

If you had 10 drives in a RAID 10, you'd be pulling data from all of them when reading, and have the writing speed of a stripe to 5 disks. With RAID 5 you still have massive calculations when writing, and you would only pull data from 9 disks when reading.

Perhaps you can give an example of why you imagine that RAID 5 would give better performance (in any scenario).

i don't know if you noticed this but your worked example omits the line 'the writing speed of a stripe to 9 disks' which answers your question some what.

i don't think anyone would use RAID5 with 10 disks would they? and of course there's capacity too.

[Loobster]

Originally Posted by Maxatoria

raid's job isn't about performance but about maintaining the data in the event of a drive failure

Not true.

RAID can be used for a number of reasons.

I spec RAID 10 over RAID 5 for my customers precicely for performance reasons.

[Loobster]

Originally Posted by flagpole

i don't know if you noticed this but your worked example omits the line 'the writing speed of a stripe to 9 disks' which answers your question some what.

i don't think anyone would use RAID5 with 10 disks would they? and of course there's capacity too.

I see your point, but with the parity calculations needed to even figure out what is written to a RAID 5 set, the performance isn't likely to get near to writing to a RAID 10 set.

I'm sure someone has a RAID 5 set with 10 disks, somewhere. Especially when you think that companies that need a lot of data space use storage units that can accomodate up to 15 or 18 hard drives.

[Keiō Line]

For backup servers raid 5 is perfectly adequate, and in most cases raid 10 is simply a waste of resources. There are many areas where performance is not that much of an issue, including file servers for users (assuming typical use). A file taking three seconds to open instead on one second, is nothing to be concerned about in most work environments.
(obviously we are talking word files etc, and not oracle databases)


Hang on to your hats here guys, but sometimes the performance gain of raid 10 over raid 5 is not that great
http://www.s3s.eu/files/documents/h5...vs-sata-wp.pdf
(sata - hardware raid NOT SW raid as advertisezed on most motherboards)

SSD are small in capacity and high in price so you could end up having to choose raid 5 for financial reasons, especially when you factor in the cost of expansion units to house all your extra disks.

Finally if "raid 5" was a a dead technology, why is "raid 6" becoming so popular?

[c4rv]

Originally Posted by Keiō Line

For backup servers raid 5 is perfectly adequate, and in most cases raid 10 is simply a waste of resources. There are many areas where performance is not that much of an issue, including file servers for users (assuming typical use). A file taking three seconds to open instead on one second, is nothing to be concerned about in most work environments.
(obviously we are talking word files etc, and not oracle databases)


Hang on to your hats here guys, but sometimes the performance gain of raid 10 over raid 5 is not that great
http://www.s3s.eu/files/documents/h5...vs-sata-wp.pdf
(sata - hardware raid NOT SW raid as advertisezed on most motherboards)

SSD are small in capacity and high in price so you could end up having to choose raid 5 for financial reasons, especially when you factor in the cost of expansion units to house all your extra disks.

Finally if "raid 5" was a a dead technology, why is "raid 6" becoming so popular?

you have to remember that for applications such as file servers that disk performance far exceeds the performance of the network.

Also fewer servers are using internal disk any more with the general move to NAS for low end devices and SAN for higher end requirements.

[Loobster]

Originally Posted by Keiō Line

For backup servers raid 5 is perfectly adequate, and in most cases raid 10 is simply a waste of resources. There are many areas where performance is not that much of an issue, including file servers for users (assuming typical use). A file taking three seconds to open instead on one second, is nothing to be concerned about in most work environments.
(obviously we are talking word files etc, and not oracle databases)


Hang on to your hats here guys, but sometimes the performance gain of raid 10 over raid 5 is not that great
http://www.s3s.eu/files/documents/h5...vs-sata-wp.pdf
(sata - hardware raid NOT SW raid as advertisezed on most motherboards)

SSD are small in capacity and high in price so you could end up having to choose raid 5 for financial reasons, especially when you factor in the cost of expansion units to house all your extra disks.

Finally if "raid 5" was a a dead technology, why is "raid 6" becoming so popular?

As c4rv hinted at, you evidently aren't familiar with modern RAID usage and performance in an enterprise network environment.

Your arguments don't make sense.

If you have budgetary constraints, then you aren't selecting SSDs in the first place, rather than using SSDs in a RAID 5 over RAID 10.

And most servers that use RAID are not 'backup servers'. Saying that 'in most cases RAID 10 is simply a waste of resources' just tells me that you aren't familiar with what the purpose of server usage or requirements are in 'most cases', but that you imagine that the cases you have been involved with are typical of the average environment.

I realise that this isn't what this thread was about at the start, but since we've moved onto general RAID principles ....

[Keiō Line]

Originally Posted by Loobster

As c4rv hinted at, you evidently aren't familiar with modern RAID usage and performance in an enterprise network environment.

I am more than familiar with RAID usage in some enterprise networks, as well as being familiar with self proclaimed IT gurus and the disparity between what they claim to know and what they do know.

Originally Posted by Loobster

Your arguments don't make sense.

We shall see

Originally Posted by Loobster

If you have budgetary constraints, then you aren't selecting SSDs in the first place, rather than using SSDs in a RAID 5 over RAID 10.

Budgetary constraints don't mean "cheapest solution". Someone may come asking for the quickest disk solution giving them X amount of storage for Y pounds (obviously other factors such as redundancy need to be considered, but rarely by the end user).
If they need 1TB of storage and can afford a raid 5 SSD solution, but not a raid 10 for their "Y pounds", then they should go for that.
(given the high price and low capacity the scenario is all to common).

Originally Posted by Loobster

And most servers that use RAID are not 'backup servers'. Saying that 'in most cases RAID 10 is simply a waste of resources' just tells me that you aren't familiar with what the purpose of server usage or requirements are in 'most cases',

I never said that most servers that use raid are backup servers. I was giving the most basic of examples as to when raid 5 is perfectly adequate.

I then went on to discuss other situations where a raid 10 would be faster but the performance hit in going to a raid5 would not be significant.

Originally Posted by Loobster

but that you imagine that the cases you have been involved with are typical of the average environment.

I would never be so arrogant as to assume this.

[Loobster]

Originally Posted by Keiō Line

I am more than familiar with RAID usage in some enterprise networks

Evidently not, based on your responses.

Originally Posted by Keiō Line

If they need 1TB of storage and can afford a raid 5 SSD solution, but not a raid 10 for their "Y pounds", then they should go for that.
(given the high price and low capacity the scenario is all to common).

Nonesense.

At the current price points, and even with the temporarily inflated prices for 'rotational' drives, a RAID 10 array of spinning disks will still be faster and cheaper than a RAID 5 array of SSDs, given your 1TB [usable space] example.

Either you can't do maths, or you just guessed that you'd be right without even bothering to do any sums.

Originally Posted by Keiō Line

I then went on to discuss other situations where a raid 10 would be faster but the performance hit in going to a raid5 would not be significant.

Anyone familiar with RAID knows that the performance hit going from RAID 10 to RAID 5 absolutely IS significant (especially writing).

[BlizzardUK]

Thanks everyone for the info. I am looking now for a hardware based card with onboard memory to do the hard work for a RAID 5 array. I am going to hook up 5 3TB drives, I can't afford 8 of them (to get the 4x 3TB that I need), so will have to make do with RAID 5 over RAID 10. This wouldn't be server based, just home desktop PC based to keep my storage files safe as I have never had more than 1 drive fail at the exact same time. I won't be using SSD with it, as my SSD will be my OS drive only.

I would only have about £130 max to spend on the card though, is this asking a miracle for a 5 port hardware controller ? I can only see software based cards which don't seem to be much good for RAID 5.

[Keiō Line]

Originally Posted by Loobster

Evidently not, based on your responses.

Well we will see about that.

Originally Posted by Loobster

Nonesense.

At the current price points, and even with the temporarily inflated prices for 'rotational' drives, a RAID 10 array of spinning disks will still be faster and cheaper than a RAID 5 array of SSDs, given your 1TB [usable space] example.

No it wont. Maybe sequential reads and writes SAS may edge it, but for random reads and writes SSD in RAID5 will wipe the floor with SAS raid 10.

Originally Posted by Loobster

Either you can't do maths, or you just guessed that you'd be right without even bothering to do any sums.

I haven't done the "math", because my experince tells me I have no need.

Originally Posted by Loobster

Anyone familiar with RAID knows that the performance hit going from RAID 10 to RAID 5 absolutely IS significant (especially writing).

Depends in what environment. As I said there WILL be a hit in performance, but it is the user experience that would determine if the loss or gain is significant or not.

[Esot-eric]

For home use hardware-based RAID is total overkill. Not to mention if the card dies you'll need to shell out for a new one of the same model or lose your data. There is very little hard work required for RAID5, it certainly wouldn't strain even the lowest-end Atom processor available today.

Go for pure software RAID using the SATA ports in the machine (and maybe a cheap SATA PCI-E card if you need more ports). I think even Windows supports some kind of built-in RAID, but of course FreeNAS (RAIDZ) or Linux will do it for free.

[BlizzardUK]

Originally Posted by Esot-eric

For home use hardware-based RAID is total overkill. Not to mention if the card dies you'll need to shell out for a new one of the same model or lose your data. There is very little hard work required for RAID5, it certainly wouldn't strain even the lowest-end Atom processor available today.

Go for pure software RAID using the SATA ports in the machine (and maybe a cheap SATA PCI-E card if you need more ports). I think even Windows supports some kind of built-in RAID, but of course FreeNAS (RAIDZ) or Linux will do it for free.

There seems to be conflicting reports then. So in your opinion RAID 5 is fine for cheap SATA RAID card and on-board ? Maybe I have been reading old posts. I will be getting a i7 3770K with 8gb ram, would this be slowed down at all by the RAID ? As I need fast CPU speed due to video encoding, although I wouldn't be outputting the files to the RAID drives as it is not uncompressed, so I am unsure if they are only a drain when in use ?

So for instance, if I was to use RAID 5 with on-board or cheap card, then my CPU will not be slowed down if it is not being written to ? If it is, then how much of a slow down would be noticed ?

[Maxatoria]

Originally Posted by BlizzardUK

Thanks everyone for the info. I am looking now for a hardware based card with onboard memory to do the hard work for a RAID 5 array. I am going to hook up 5 3TB drives, I can't afford 8 of them (to get the 4x 3TB that I need), so will have to make do with RAID 5 over RAID 10. This wouldn't be server based, just home desktop PC based to keep my storage files safe as I have never had more than 1 drive fail at the exact same time. I won't be using SSD with it, as my SSD will be my OS drive only.

I would only have about £130 max to spend on the card though, is this asking a miracle for a 5 port hardware controller ? I can only see software based cards which don't seem to be much good for RAID 5.

don't view raid as a backup medium its just an extra layer to keeping your computer up like having a UPS will help against power blips but wont help if they turn off the power for good and also it doesn't protect against things like psu's going tits up and frying everything connected to it or even things like oops i deleted the wrong file so wheres my backup copy

and as for the 10 v 5 debate theres plenty of life left in it as raid 5 will win on physical space/heat/power consumption which may be of concern to data centre managers and also if you have a server that mainly serves a site on a slow link theres no point speccing something that will spend 90% of its time waiting for the link