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SATA vs RAID0+1

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Mico

Member
Joined
Aug 3, 2002
Location
Marrietta, GA
512mb dual channel PC3200 crucial RAM
Athlon XP 2800+ (new barton core)
Asus A7n8x

Now...which would run faster?
1: 120G 7200rpm SATA HDD
2: 2 60G 7200rpm RAID0+1
 

Pla

Member
Joined
Apr 24, 2002
Location
San Francisco, CA
There is no question. It is like the question which is faster: 1 disk or raid-0?

Raid 0+1 is basicly raid-1 using 4 disks. So with 2 disks you have 2 options for raid: raid-0 and raid-1

1) Raid-0 (striping)
It devides the data on equal blocks (stipes) and saves them on different phisical hdds.
If you use the 2 new hdds (asuming same size) you will get twice the read and twice the write speed.
As reliability - it iwll be almost the same as of a single drive (a little worse) so you will still need to back up but your editing performance will be faster.
You don't loose any space.
You can use 2, 3 or 4 dirves.

2) Raid-1 (mirroring)
Everything is saved to both disk by duplicating. So if 1 disk fails you can replace it with new and reatore the raid array.
The reliability is very good (the chance of both drives failing simultaneously is very small). However you loose space - the total space will be half as if you didn't use raid-1.
The write speed is the same as a single drive. However the read speed is twice faster of a single drive.
You can use 2 or 4 dirves.

The latency/seek time is the same.
The bandwidth is usualy doubled for 2 drives.

My single drive had 50/36 MB/s read/write bandwidth and with raid-0 it is now 99/69 MB/s which is 1.98 times faster.

If you use 3 drives it will be almost 3 times faster. However in real life the bus gets saturated at around 150 MB/s so even with 3 drives you will get more like 2.6 times instead of 3. And for 4 or more dirves you will not get over the 150 MB/s maximum.

SATA vs PATA
This is asuming PCI bus. When we get PCI express things will change. SATA or ATA 133 doesn't matter for the overal PCI bus maximum. It matters only for the transfer time between the hdd cache and the controler.
When using single drive ata/133 and you have cache hit the speed will be 133 MB/s comared to 150 MB/s on SATA.
When using raid and you have cache hit the speed on both will be the PCI max of 150 MB/s (instead of 300 SATA and 266 ATA). So for raid it doesn't matter if you use SATA or ATA.

Also SATA has benefit only when on cache hits. Disk media transfer is way bellow 133 MB/s. Current 7200 rpm drives usualy have media transfer rate of about 50 - 60 MB/s