Hey there folks.

Just wanting some expert opinions on whether I sould go Raid or not.

Got a samsung spinpoint F1 750GB hdd at the moment and considering getting another one and running them in Raid.

I know about reliability issues and will be performing regular backups.

Just wanting faster boot-up times and generally faster read/write to the hdd really. Although the one on its own isn't exactly sluggish there's room for improvement.

What do you thing guys?

Phil

In my opinion i avoid RAID, don't like the idea of losing two HD's worth of data if one dies. When i tried it seems the performance gains were negligible anyway. If you're after faster boot up times why not get a small capacity 10k drive or solid state drive for a boot drive?

Don't want the noise of a 10k and solid state is expensive and isn't it actually slower than a decent SATA drive?

Phil

TBH, your bootup time will be influenced far more by what you have running and how much you optimise your services and startup than the drive speed. I take it by RAID you were referring to a 2 disk RAID 0 or 1 array? Vista's 'Readyboot' functionality tries to wring a speed boost using a solid state drive in conunction with the normal one, but in my experience does bog all worth writing home about.

I assume you're thinking of RAID 1 so the data is striped, so you get theoretically faster reads?

Not worth it for a home PC IMO. You'll only see a gain with biggish files and even then very controller-dependent. As already said, reduce the number of startup services or buy a 10k drive. Also as I'm sure you appreciate you get an increased risk of failure.

Yes i was thinking of RAID1.

Would probably help when editing videos and moving the big files around etc.

Also games will load faster I'm sure.

Will have a look at costs etc and see what I think.

Thanks

Phil

Video editing is one area that might benefit, as the files are large.

Forget about raid. Writing and reading to one drive is deffo faster than doing likewise with 2, unless you have serious money for serious hardware. The main benefit of raid is redundancy (not backup). Save your money, buy a poppy, flowers for your loved one and still have change in your pocket. Just my 2 cents.

What RAID Level are you talking about?

I assumed RAID 0 from the way you put it but there are also 1,2,3,4,5,6 and n to consider and looking a bit further down you have said RAID1.

RAID 1 duplicates all your data to give you a certain level of data protection and also improves read performance in cases where you are loading multiple files at the same time. This obviously being because you can read both at the same even with todays basic controllers. You will also improve read times when reading larger files but what you mean by larger depends on the sector size of the disc etc.

There is also potential to reduce write performance, but any half decent raid card/chipset should allow you to do the write then offload this. On a motherboard where there isn't battery backup, then you would probably get a write hit unless you were prepared to use write back caching rather then none or write through.

So next myths to dispel:

- 10k drives are faster.

Cobblers.

Some 10k drives are faster under some circumstances but they are often not.

A 7200rpm drive with a large cache (32MB on the 750GB F1 drives), a high data density

and NCQ will wipe the floor with many 10k drives.

This is usually the case for sequential reads and writes because the data is more dense you can write more MB per inch covered and even though the disk is only spinning at 72% of the speed if the slower drive writes 50mb per inch and the faster drive writes 25mb per inch it is obvious the slower drive has better sequential throughput.

The advantage for the 10k drive is in seek time, but how many times does a home user do truly random data transfer? It's rare unless the drive is seriously fragmented. You want to load a file, so the drive will go off and read it from usually sequential blocks.

- Flash will replace HDD right now.

In some circumstances flash can give a performance gain however this isn't a given.

For example if you want to read a whole chip of sequential data flash can be quite good, but writing just one or two bits in a flash chip is very poor.

Why? This is because to write to the flash chip you have erase some or all of the chip when you write to it. This some size will be bigger than just a couple of bits or bytes so you are doing the following:

- Read all the data you're going to erase

- Erase all the data in the area of the chip you want to write

- Modify the read data to the correct data

- Write it all

- Verify the write

Often while writing a chip like this you can't read or write to the whole chip or at least the section you are writing to.

Flash chips have a limited number or write cycles usually between 100k and 1million per bit. If you look at what I put above you will realise that every time you write a single bit there are at least two writes (erase and write) and that is for the whole chunk you wish to write not just the bit you do.

Flash chips are also expensive at the moment per GB compared to Mechanical disk.

Flash chips are not always lower power.

If a flash drive uses 5W when active and nothing when not, this means whenever you are reading or writing it is using 5W.

Compare this to a hard disk which we will say in this case uses 10W maximum. That 10W is only at spin up from standstill or when the head is seeking all over the place. Most of the time the drive will not be seeking and could be just spinning along maintaining speed and maybe using 2W.

So a in a situation where the disk is reading/writing sequentially it could be using less power.

Also add the fact that some manufacturers now have hard drives that can vary their spin speed depending on demand and so when not much is being done they will run slower and only speed up when the performance is needed.

I assume you're thinking of RAID 1 so the data is striped, so you get theoretically faster reads?

Not worth it for a home PC IMO. You'll only see a gain with biggish files and even then very controller-dependent. As already said, reduce the number of startup services or buy a 10k drive. Also as I'm sure you appreciate you get an increased risk of failure.

RAID 1 is not striped data that is RAID 0

RAID 0 = Striped

RAID 1 = Mirrored

You are correct however in saying that RAID 0 is often only good when you are working with large files so you can write a chunk to each disk at the same time and reducing write times.

For reads you have a potential disadvantage as you are having to potentially pull a single file off two or more discs and then reassemble the data in the correct order before passing it upwards. Of course with reads there is also a potential advantage in certain quite specific circumstance as you have multiple spindles to read data from so can pick two small files up from two completely associated areas of disk at the same time.

RAID 1 can have a nice advantage for read throughput, as you can read data from two disks so lots of non sequential reads can be serviced more quickly than on a single disk of the same type.

RAID 1 can potentially also introduce an performance hit for writes as you have to have the data written to two or more discs. Some controllers will take care of this and do the work for you, so negating this, but most that you will find on a motherboard don't have battery backup or large amounts of RAM so can't cache the data safely so have to carry out at least one of the writes. However saying this modern drives have quite large write caches so this is probably less noticeable than it may once have been in most circumstance that an average home user will see.

Forget about raid. Writing and reading to one drive is deffo faster than doing likewise with 2, unless you have serious money for serious hardware. The main benefit of raid is redundancy (not backup). Save your money, buy a poppy, flowers for your loved one and still have change in your pocket. Just my 2 cents.

As pointed out the section I have put in bold is incorrect for the reasons given.

In some instances it can be faster or slower, but each one is quite specific. For RAID 1 reading lots of files will almost always be faster than from a single disk.

I do agree with your final sentiment of save the money unless you want it for data redundancy in the even of a single disk failure.

Edited 7 November, 200817 yr by cheezemonkhai

Yes i was thinking of RAID1.

Would probably help when editing videos and moving the big files around etc.

Also games will load faster I'm sure.

Will have a look at costs etc and see what I think.

Thanks

Phil

Depends what sort of file sizes you're talking.

Striping (RAID 0) would help if you were editing very large video files, however giving your file system a larger block size. As a block is usually kept together on the dis you wouldn't have to seek to get the whole block, so a 2048k block size will mean better performance than a 512byte block size.

Depending on the file system, this also means that there is less wastage of the system when you are using large files that are as big or bigger than the block size. This is because you have less blocks and each block will contain information about it or be referred to in a lookup table etc.

Of course if you try and have lots of smaller files (smaller than the block size) on a file system with a big block size then the performance will be slower as you will be reading in an entire larger block even though there is almost no data in it. This also means that the file system would be wasting large amounts of data space with only partially full blocks.

So in short file system tuning can have much more of an effect than playing with discs.

Games will use lots of small files and Video a few large files. These two are not usually good on in combination as what is good for one will be poor for the other.

RAID 0 isn't, IMHO, going to help you games load faster such that you will notice.

In a computer system the human is the slowest device in the system

So my 2p worth.

Faster boot up times:

You have a few options, tune your file system to suit the files, tune your system start up and OS to load less at boot, get the system to use suspend to disk (hibernate) as you would then not need to load the whole OS.

Another option that would see most improvement would be to buy a small flash drive (8/16BG) and put your OS on this.

If you do this you MUST put your swap file on a hard drive along with all regularly updated chunks of the OS such the index files or turn off indexing which would slow down searches. Just put the bare OS on here and nothing else.

Then put the applications etc on your nice big fast disk.

As for faster game loads etc... well you could always buy a bucket load of RAM and create a RAM disk then have the game you use most copied into the RAM disk when you boot.

Of course this probably wouldn't have any advantage because once you've run something it is cached in RAM anyway for a bit so may be quicker the second time around and also if you just used the RAM as RAM your OS would be paging less so quicker.

Thanks. Plenty of food for thought there!

As you said about the RAID controller not having much memory available to cache files I doubt that would be a problem as there would be 64mb available across both disks.

Will do some searching around and will probably consider the flash drive idea!

Thanks

Phil

I've got a stripped array as my boot drive, with two WD Raptors.

Not noticed a difference really!

If you decide to go Raid 0 then ensure you have a good regular proven backup regime in place because you are doubling the chances of losing all your data. I found Raid 0 helped my old pc no end, although I have not bothered with the current one.

I dont see the point really, as it just increases the need for redundancy and unless youre a real power user i doubt you would notice the difference. As stated before if you want faster boot up times use a small HDD as a designated boot drive and nothing else, along with fine tuning the windows boot.

RAID 1 is not striped data that is RAID 0

RAID 0 = Striped

RAID 1 = Mirrored

fsck it. I *always* get them the wrong way round...

Probably not worth the effort and cost.

Raid 5 gives you the best of both worlds with speed and redundancy but that's getting a bit silly for your house.

Money better spend elsewhere IMHO.

Probably not worth the effort and cost.

Raid 5 gives you the best of both worlds with speed and redundancy but that's getting a bit silly for your house.

Money better spend elsewhere IMHO.

Ahh but Raid 5 can only deal with a single dead disk

Thanks. Plenty of food for thought there!

As you said about the RAID controller not having much memory available to cache files I doubt that would be a problem as there would be 64mb available across both disks.

Will do some searching around and will probably consider the flash drive idea!

Thanks

Phil

I am talking about cache for the RAID controller not the disk cache.

When you're writing things to multiple disks a good RAID chip can take the write once, store it in battery backed RAM and then go off and do all the multiple writes as and when. This means that as far as your drivers are concerned the write was done in one hit, even if the controller with it's cache is done in many goes.

The drive cache only comes in when the drive has the data for writing or has streamed the data it thinks you want next into the cache for a fast read.

That 64MB (2*32MB) cache on your drive would make no difference to the write hit as your raid controller would still have to take the data, send a write to each drive, wait for the drive to confirm the write and carry on with the next bit.

It isn't a given that this will happen and the cache on the drives might make it less likely that the controller would have to wait while doing a write but it isn't the same cache I'm talking about.

IMHO, think 512MB, 1GB or more of RAM with a battery backup unit for controller cache on a performance card.

Ahh but Raid 5 can only deal with a single dead disk

Raid DP then :P

fsck it. I *always* get them the wrong way round...

If you remember that RAID is Redundant Array of Inexpensive Disks, remember the first bit, Redundant.

A striped array gives you no redundancy, hence the RAID level is 0.

A mirrored array gives you one level of redundancy, hence RAID 1

But don't apply that to other RAID levels

Just to throw a spanner in the works....

Previously i had 2 old-skool 36gb raptors striped for my O/S and that was definately benificial compared to the WD-AAKS i have now... probably not much in out and out transfer speeds.. but it just made the OS feel snappier, probably because vista is quite a fan of background I/O...

Which WD-AAKS is it you have?

Is it one of the energy efficient models? If so that might explain a few things if you have a read into it.