expalin raid and sata to me

[raggie33]

ok i put to sata drives in raid striping but there is numbers to set it to something like 128 bit or something werd word like that what number is the fastest?.also how many dirves can each sata port have on it? i read the stuff but dont understand it all that well

 

[IlluminatingBikr]

SATA is a format, that is replacing the old IDE, large ribbon cables. The IDE cables are wide, like a wide freeway, but they are slow. SATA is a narrow highway of information, but it's a super-highway...it goes really fast.

There are different RAID setups. RAID 0, 1, 0+1, 5, 15, etc.

Data striping is RAID 0, in which each drive stores about half of the information. Say you have a 10 MB file. Instead of taking the time to write all 10 MB, each drive only writes 5MB. This can be dangerous if you lose either of your drives.

 

[DarkLight]

you set the striping size depending on the intended use of the array.
I personally use 16k striping for performance on smaller file sizes.. each sata port can handle one drive only.

32 or 64k striping is a good middle ground if you are unsure of what size to use.

be sure to load your SATA drivers off floppy by pressing f6 during windows install when it asks you to.

Right now there is not a large difference in performance between PATA and SATA but SATA will gain ground in the future rapidly.

 

[turbodog]

[ QUOTE ]
IlluminatingBikr said:
SATA is a format, that is replacing the old IDE, large ribbon cables. The IDE cables are wide, like a wide freeway, but they are slow. SATA is a narrow highway of information, but it's a super-highway...it goes really fast.



[/ QUOTE ]

Ultra ata --> 133 speed
serial ata --> 150 speed

Not a lot of difference. And these a controller to drive transfer speeds, which are way above transfer rates to the drive platters.

Now, with that said, I have been using some western digital enterprise class sata drives lately. 8 meg cache, 10k rpm, and a 5 year warranty. They are not cheap, but they smoke. They'll give a 15k rpm lvd scsi drive a run for its money.

 

[idleprocess]

RAID 0 offers fast read times since you can read from 2 drives at once.

RAID 1 mirrors drives. It's the least efficient fault-tolerance.

RAID 2, 3, & 4 aren't used anymore from what I can gather.

RAID 5 is the most efficient fault-tolerance. A RAID5 array must have at least 3 disks. The capacity of a RAID 5 array is N(number of disks) x C(disk capacity) - C. You lose one disk worth of capacity for the redundancy, and can lose one disk without losing data. Usually, if you lose a disk in an array, the array will rebuild itself when you replace the fallen disk.

RAID 10 is mirrored RAID 5 arrays. Inefficient, but it offers greater capacity

 

[raggie33]

i know its a lot faster then my single maxtor 80 gig 8 meg cache drive average like 90megs per second.but had data couption. im useing the controler on my nforce 3 mobo its a gigabyte ga-k8ns.i updated the raid and sata drivers to 5.10.2600.507 hopefully thats fixes problem they was relased in janery

 

[turbodog]

[ QUOTE ]
idleprocess said:
RAID 0 offers fast read times since you can read from 2 drives at once.

RAID 1 mirrors drives. It's the least efficient fault-tolerance.

RAID 2, 3, & 4 aren't used anymore from what I can gather.

RAID 5 is the most efficient fault-tolerance. A RAID5 array must have at least 3 disks. The capacity of a RAID 5 array is N(number of disks) x C(disk capacity) - C. You lose one disk worth of capacity for the redundancy, and can lose one disk without losing data. Usually, if you lose a disk in an array, the array will rebuild itself when you replace the fallen disk.

RAID 10 is mirrored RAID 5 arrays. Inefficient, but it offers greater capacity

[/ QUOTE ]

Raid 1 is also one of the (if not THE) fastest read performances out there.

Raid 10 is really 1+0 or 0+1. It is a striped mirror, or mirrored stripe. It's not a mirrored raid 5. It is extremly fast. I have used several, and they will amaze you if setup properly.

Raid 5 can really suck at performance. Every raid 5 machine I have seen, and that includes some $25,000 dell and compaq servers has really been crummy performance numbers.

But back to the question at hand...... set it for the default stripe block. 32 or 64 are fine. You're likely not gonna notice a difference in either case.

 

[idleprocess]

RAID5 is slow on write - it has to write to multiple locations for every byte. It could theoretically offer good read performance since data exists in more than one physical place, similar to a mirror set.

There used to be a term for mirrored RAID5 arrays. Perhaps the technique has fallen out of favor, so it's no longer used.

I don't think there's a RAID technique out there that enhances write performance.

 

[turbodog]

Re: explain raid and sata to me

[ QUOTE ]
idleprocess said:
RAID5 is slow on write - it has to write to multiple locations for every byte. It could theoretically offer good read performance since data exists in more than one physical place, similar to a mirror set.

There used to be a term for mirrored RAID5 arrays. Perhaps the technique has fallen out of favor, so it's no longer used.

I don't think there's a RAID technique out there that enhances write performance.

[/ QUOTE ]

For the record, there are obscure raid #s above 10...... they run all the way to about 100 or so.

The ONLY time I saw a raid 5 array that worked worth a darn was an OLD compaq array using scsi drives. The drives themselves were not high performers, but they had an obscure scsi command called spindle synch. This kept the rpm of all drives exactly the same and each platter was also in exact relation to each other. This kept i/o requests from having to wait for 8 drives to position to the proper location. Needless to say, this was not a cheap server.

Write performance has been supplemented a lot by the o/s nowdays. I really like how server 03 will run when you throw hardware at it.

The whole speed thing is really getting to be a non issue. I sold an external, consumer-level, cheap usb/firewaire hard drive. It would easily sustain transfer rates of 20 megabytes/second for as long as your wanted. The best drives anywhere could not do this 3-4 years ago.

Drive space and speed are fast outrunning storage requirements. I mean you can buy .5T drives now.

 

[IlluminatingBikr]

[ QUOTE ]
turbodog said:
[ QUOTE ]
IlluminatingBikr said:
SATA is a format, that is replacing the old IDE, large ribbon cables. The IDE cables are wide, like a wide freeway, but they are slow. SATA is a narrow highway of information, but it's a super-highway...it goes really fast.



[/ QUOTE ]

Ultra ata --> 133 speed
serial ata --> 150 speed

[/ QUOTE ]

Turbodog,

Individually, isn't each lane (wire) of the highway (cable) is working a lot faster in SATA than in PATA?

 

[turbodog]

If you're saying that the individual wires carry more data than parallel, then yes. But the transfer speed from host to drive is still only a tad faster. These signals travel at near light speed anyway...... it's not like sata will "get there faster" or anything.

 

[DarkLight]

the drive interface is still faster than the head/disc combination at any rate. ATA or SATA....

fast drives are lucky to put out 45mb/sec sustained..
many are far less..

(I have two WD raptors in raid zero)

 

[turbodog]

wd raptor..... nice drive

 

[idleprocess]

A quick glance at ATA transfer specs will tell you how utterly meaningless they are for gauging real-world performance.

Back when people were excited about ATA-66 and ATA-100, the spec was a measurement of data transfer between buffers for 2 milliseconds... and I think the buffers were pre-loaded with data at the time of the "speed measurement."

Needless to say, there were few if any hard drives that could sustain anything close to that kind of transfer rate for any signifigant stretch of time back then.

I don't understand the hype behind SATA, myself. Parallel data transfer has the advantage of using multiple simultaneous paths for data, so you can use multiple slower (cheaper) transceivers and not be so sensitive to interference, unlike serial transfer. Unless there's some pressing issue with increasing PATA throughput, I don't understand the motivation for SATA. Serial is best for long-haul transmission (networks) or where a reduction in traces/lines is essential, like embedded apps.

I've heard that SATA is more prone to interference than PATA. The cables are certainly lower-profile, but the connectors look a bit more fragile. I don't understand why so many SATA harddrives have special power connectors. My understanding is that they jusst use the same +5V and +12V as other drives.

/ubbthreads/images/graemlins/icon3.gif

 

[turbodog]

[ QUOTE ]
idleprocess said:
A quick glance at ATA transfer specs will tell you how utterly meaningless they are for gauging real-world performance.

Back when people were excited about ATA-66 and ATA-100, the spec was a measurement of data transfer between buffers for 2 milliseconds... and I think the buffers were pre-loaded with data at the time of the "speed measurement."

Needless to say, there were few if any hard drives that could sustain anything close to that kind of transfer rate for any signifigant stretch of time back then.

I don't understand the hype behind SATA, myself. Parallel data transfer has the advantage of using multiple simultaneous paths for data, so you can use multiple slower (cheaper) transceivers and not be so sensitive to interference, unlike serial transfer. Unless there's some pressing issue with increasing PATA throughput, I don't understand the motivation for SATA. Serial is best for long-haul transmission (networks) or where a reduction in traces/lines is essential, like embedded apps.

I've heard that SATA is more prone to interference than PATA. The cables are certainly lower-profile, but the connectors look a bit more fragile. I don't understand why so many SATA harddrives have special power connectors. My understanding is that they jusst use the same +5V and +12V as other drives.

/ubbthreads/images/graemlins/icon3.gif

[/ QUOTE ]

I would hazard that it's a cost issue.

 

[r2]

SATA:

Serial buses don't require the strict synchronization between parallel wires that parallel buses do. This means they can work more reliably and at higher speeds over greater distances. PATA was really limited by short cables, and to go faster it would need even shorter, better shielded cables. SATA has a lot more room for bandwidth growth than PATA.

It's similar to old parallel connections for printers, etc., which had stricted limits on how long the cables could be, and have since been replaced by USB and FireWire, both serial connections.

RAID:

Originally, RAID was defined with levels 1--5. RAID0 isn't really RAID (which originally meant Redundant Arrays of Inexpesive Disks) because there isn't any redundancy--it just stripes the data over multiple disks so you can read fast in parallel. It makes your data considerably more vulnerable, though.

RAID5 is slower at reads than RAID1 because it uses error coding. You have to wait for some subset of the disks to all find the right blocks which can then be recombined into your data, whereas RAID1 is done when the first disk finds a block (since they are just mirrors of each other). RAID5 is more efficient with space but slower at reads, and it requires more than 2 disks. Your data all survives a single disk failure in RAID1 and RAID5.

If you really want to understand what's going on, check out the original RAID paper:

RAID paper

- Russ

 

[raggie33]

my sata drives where only 50 bucks a pop they have both power conecters.and there prerrty darn fast.but there only 60 gigs a peice.which sucks but realy i seldem have over 15 gigs used.and in sata striped i get a average of 90 megs per second thats not to bad i guess.i also hate them old big ribon cables.

 

[raggie33]

hey can some one aswer thease 2 questions (1) this is there a sata cable that can conect to drives to each conecter so i can use 4 drives in raid?(2) can i add in my old pata drive to the sata raid i have?my sata drives are maxtor 60 gigs with 8 megs cache .the old rata is 80 megs with 8 megs a cache

 

[gessner17]

No, with SATA you are restricted to 1 drive per channel. There is no way to connect PATA to the SATA controller.

 

[raggie33]

nah i now ya cant add the pata to the sata.what i mean is in my mobo bios ya can add the pata drive to a raid config to.so wht iean is can it be in the sata raid setup.lol i doubt my question is makeing sence.