RAID 0+1 faster than RAID5

[BoB-O TiVo]

Hey all,

I know "faster" can mean lots of things, but, in general, am I better off using RAID 0+1 or RAID5 for maximum performance? I want some sort of redundancy and I'm trying to decide if I need to bust out the cash for a uber-controller for RAID5.

Thanks,
BoB

 

[DougLite]

For multi user performance, RAID 0+1 is indeed faster than 5. Requests tend to be shorter but more frequent and random in a multi user server environment. Good server level controllers allow data to be read from both halves of the array and the fewer drives in each stripe mean that fewer spindles are required to complete a given request.

On the desktop or in media storage however, things are a little different. A RAID-5 array with five drives can use the higher number of spindles in the stripe to increase linear transfer performance. If you are doing media streaming/transferring, RAID-5 is probably the way to go, as that gives you the capacity of the third drive in the array rather than just the first two in a 0+1 array.

You will see lower CPU utilization on a 0+1 array, especially during writes - unless you get a controller with hardware accelerated XOR engine. If the box is a dedicated file server, this is largely irrelevant. Even software RAID-5 can deliver good performance on a deidicated file server.

 

[BoB-O TiVo]

For multi user performance, RAID 0+1 is indeed faster than 5. Requests tend to be shorter but more frequent and random in a multi user server environment. Good server level controllers allow data to be read from both halves of the array and the fewer drives in each stripe mean that fewer spindles are required to complete a given request.

On the desktop or in media storage however, things are a little different. A RAID-5 array with five drives can use the higher number of spindles in the stripe to increase linear transfer performance. If you are doing media streaming/transferring, RAID-5 is probably the way to go, as that gives you the capacity of the third drive in the array rather than just the first two in a 0+1 array.

You will see lower CPU utilization on a 0+1 array, especially during writes - unless you get a controller with hardware accelerated XOR engine. If the box is a dedicated file server, this is largely irrelevant. Even software RAID-5 can deliver good performance on a deidicated file server.

The big question is whether or not it's worth getting a good raid card for RAID5 or just use the Sil3114 on the Asus A8N-SLI Premium for RAID 0+1? I write software and edit video ripped from my TiVo.

BoB

 

[DocFaustus]

The big question is whether or not it's worth getting a good raid card for RAID5 or just use the Sil3114 on the Asus A8N-SLI Premium for RAID 0+1? I write software and edit video ripped from my TiVo.

BoB

I believe one of the two raid controllers on your Motherboard already supports RAID 5.

 

[StoneNewt]

This basically paraphrases DougLite but, a cheaper RAID5 card (hpt1820) will often out perform an on-board RAID0+1 for read performance however its write performance will leave a lot to be desired. The top-of-the-line 3ware RAID5 controllers often out perform software RAID0+1 with the same number of drives.

 

[BoB-O TiVo]

I believe one of the two raid controllers on your Motherboard already supports RAID 5.

Yes, but for RAID5, they are, in a word, shite. You need to spend at least $300 to get a really good hardware RAID5 card. Since that's more than the cost of another 300GB drive, I was toying with the idea of running 0+1. I'm just wondering if the performance is there.

BoB

 

[StoneNewt]

Yes, but for RAID5, they are, in a word, shite. You need to spend at least $300 to get a really good hardware RAID5 card. Since that's more than the cost of another 300GB drive, I was toying with the idea of running 0+1. I'm just wondering if the performance is there.

Okay I'm using MaxLine III 300GB w/16MB cache here.
On-board RAID controllers & software RAID0+1 (you'd also have to JBOD 2x arrays if you want to go beyond 4 drives) prices you at 77p/GB.

3ware 9500-8 >70MB/s read and writes with 8 drives & is probably the most expensive card you're gonna buy:
3 drives/600GB it's 103p/GB
6 drives/1.5TB, 72p/GB
8 drives/2.4TB, 55p/GB

Now if write speed isn't important you're looking at the HPT1820A, for a 6 drive array I'm getting 10<35MB/s writes with this card & read speeds can be over 100MB/s
3 drives/600GB, 99p/GB
4 drives/900GB, 66p/GB
8 drives/2.4TB, 44p/GB