Raid 5 Performance

[Luc401]

I have a Intel raid with 4 WD Red drives running at 5900 RPM. When i start to transfer a file from the array to the ssd that is in the machine, it starts off at around ~450MB/S then starts to dip down toward ~110MB/S as see in the picture. Can someone explain why this happens? Is it because its using cache at first but when the cache is filled it starts to slow down? Also the disk usage goes to 100% when doing this.

 

[Altecice]

You explained it well youself:

 

 

Is it because its using cache at first but when the cache is filled it starts to slow down

[Luc401]

You explained it well youself

Well, thats lame.

[Altecice]

Well, thats lame.

 

The onboard RAID controllers on motherboards are fine for RAID0/1 but they arent any good for anything else.... To get proper performance you need a RAID card with its own cache.

[Luc401]

The onboard RAID controllers on motherboards are fine for RAID0/1 but they arent any good for anything else.... To get proper performance you need a RAID card with its own cache.

I mean for the stuff im doing with it now, it should be fine for atleast the next couple of years.

[TheKDub]

Perhaps get a raid card? They're pretty cheap on amazon.

[Jarsky]

Thats an odd speed dip, I can sit consistant with my Software RAID5, you do not need a hardware RAID card for faster sustained transfer speeds as long as you have an OK CPU from the past 10 years. As far as performance, the main difference is that you're offloading the floating operations to your CPU/RAM for calculating parity etc..., instead of using a dedicated chip/memory on your RAID card. As far as redundancy, the parity data is stored across the drives, rather than on a cmos chip like with a hardware card.

 

As for cache, unless you've setup a dedicated cache - this shouldn't really be a factor in a large sustained transfer.

 

I'm running a Windows Software RAID5 as one of my arrays and it can sit perfectly fine at a high sustained speed and I sometimes move 100's of GB's to/from it.

 

You mention an Intel RAID, is it using Intel RST? Intel RST is notorious for causing all sorts of weird behavior with RAID's.

[leadeater]

Thats an odd speed dip, I can sit consistant with my Software RAID5, you do not need a hardware RAID card for faster sustained transfer speeds as long as you have an OK CPU from the past 10 years. As far as performance, the main difference is that you're offloading the floating operations to your CPU/RAM for calculating parity etc..., instead of using a dedicated chip/memory on your RAID card. As far as redundancy, the parity data is stored across the drives, rather than on a cmos chip like with a hardware card.

 

As for cache, unless you've setup a dedicated cache - this shouldn't really be a factor in a large sustained transfer.

 

I'm running a Windows Software RAID5 as one of my arrays and it can sit perfectly fine at a high sustained speed and I sometimes move 100's of GB's to/from it.

 

You mention an Intel RAID, is it using Intel RST? Intel RST is notorious for causing all sorts of weird behavior with RAID's.

 

Windows software RAID 5 is different to onbaord motherboard RAID 5. Even though onboard RAID is CPU assisted it's rather terrible no matter how good the CPU is. You should probably start looking in to using storage spaces next time you do a hardware/OS refresh since Microsoft don't really recommend or want anyone using the legacy software RAID.

 

Right now parity configuration in storage spaces has rather bad performance on writes but they are actively working on improving that, Server 2016 might bring something new to the table. If you have 4 disks you can use 2-way mirror and set the column width to 2 so you only lose 25% space not 50%, same applies for more disks.

 

If you try it and don't like it no problem, no guarantee everyone will like it anyway.

[Jarsky]

Windows software RAID 5 is different to onbaord motherboard RAID 5. Even though onboard RAID is CPU assisted it's rather terrible no matter how good the CPU is. You should probably start looking in to using storage spaces next time you do a hardware/OS refresh since Microsoft don't really recommend or want anyone using the legacy software RAID.

 

Right now parity configuration in storage spaces has rather bad performance on writes but they are actively working on improving that, Server 2016 might bring something new to the table. If you have 4 disks you can use 2-way mirror and set the column width to 2 so you only lose 25% space not 50%, same applies for more disks.

 

If you try it and don't like it no problem, no guarantee everyone will like it anyway.

 

Are you recommending that to me, or talking to OP?

I already do have a storage spaces configured like your suggestion using 8TB drives (in signature). My Software RAID5 is an old array from 2010 with 48,000hrs+. The point is that my old RAID also utilises SoftwareRAID (but on an HBA) same as the OP, but doesn't have the same issue of slow down, nor do other software RAID's i have. Theres something else affecting his array, the speed dip isn't normal. The point I was making is he does not need to go hardware RAID as suggested above.

 

[Andrew_C]

Off on a tangent, RAID5 is pretty much dead and buried. RAID10 is really where it's at. Both improved read and write performance. I will admit, I'm still running a RAID5 in my home lab, through lack of financial investment. 

[leadeater]

Are you recommending that to me, or talking to OP?

 

Yea it was for you, but your already using it

 

The info on Intel RST RAID was more for anyone reading it since you clearly knew the difference anyway. Plus I also wanted anyone else reading it to know that there is storage spaces now since most have no idea it exists.