Poor RAID-5 performance.

[Wauter]

Hello all,

I have setup a Windows Hyper-V server, using Windows RAID-5 over 3x2TB Crucial BX500 SSD's. (Around 500mb/s per single drive).

But then when I use Crystal Disk Mark to benchmark the entire array the write speeds are very poor. (See image).

The reads aren't up to speed either.

 

Does somebody have any advice / idea why this is so and what I can do about it?

 

This is my hardware configuration:

Motherboard: Supermicro X9DRW

CPU 1: Intel(R) Xeon(R) CPU E5-2695 v2 @2.40GHz, 12c 24t

CPU 2: Intel(R) Xeon(R) CPU E5-2695 v2 @2.40GHz, 12c 24t

RAM: 256GB DDR3

Networking: Standard copper 1gbit, 10gbit fiber possible

Storage: 3x Crucial BX500 SSD for VM data, + 1x Samsung 840 EVO for OS.

OS: Windows Server 2019 Datacenter (Fully licensed)

 

Any help would be greatly appreciated!

 

[leadeater]

Windows Software RAID 5 is horrible performance. Also don't use Disk Manager RAID configuration anymore, use Server Manager and Storage Spaces. The new method is still slow for Parity RAID though so don't get your hopes up.

 

Either use Storages Spaces Two-Way Mirror or get a hardware RAID controller with BBU/FlashCache.

 

Other question is do you actually need a single large logical volume? 3 induvial disks and data backups will work really well so long as you can use it that way,

[manikyath]

from your motherboard manual: (assuming i scored the right one...)

I-SATA 0/1 Intel SATA 3.0 Connections 0/1 (from Intel AHCI)

I-SATA 2-5 Intel SATA 2.0 Connectors 2-5 (from Intel AHCI)

S-SATA 0-3 Intel SATA 2.0 Connectors 0-3 (from Intel SCU)

 

you only have two SATA3 ports, the disks connected to the other ports will be limited to 300MB/s as opposed to 600MB/s

[Kilrah]

And the DM screenshot shows the array is currently syncing, so it's already busy.

[Blue4130]

4 hours ago, manikyath said:

)

 

you only have two SATA3 ports, the disks connected to the other ports will be limited to 300MB/s as opposed to 600MB/s

SATA 2.0 is still 20x faster that what he is getting. That's not the issue. 

[manikyath]

Just now, Blue4130 said:

SATA 2.0 is still 20x faster that what he is getting. That's not the issue. 

you've done your math wrong (gigabit vs gigabyte)

with a raid5 of 3 disks (2 disks plus parity), assuming no losses in the chain, he could get about 1.5x faster.

 

so yes.. it's not the (only) problem, but he's never gonna get theoretical max 500MB/s on his drives.

[Blue4130]

4 minutes ago, manikyath said:

you've done your math wrong (gigabit vs gigabyte)

with a raid5 of 3 disks (2 disks plus parity), assuming no losses in the chain, he could get about 1.5x faster.

 

so yes.. it's not the (only) problem, but he's never gonna get theoretical max 500MB/s on his drives.

No my math is correct. He's getting 15MB, sata 2 can do 300 MB. 20x

[manikyath]

1 minute ago, Blue4130 said:

No my math is correct. He's getting 15MB, sata 2 can do 300 MB. 20x

i'm gonna attest the writes to windows storage spaces being horrid, and this:

4 hours ago, Kilrah said:

And the DM screenshot shows the array is currently syncing, so it's already busy.

 

[Blue4130]

Just now, manikyath said:

i'm gonna attest the writes to windows storage spaces being horrid, and this:

 

I agree, that's why I questioned you bringing sata into this. It's not a sata problem. 

[manikyath]

Just now, Blue4130 said:

I agree, that's why I questioned you bringing sata into this. It's not a sata problem. 

it's not the (only) problem, but if it's not mentioned it's probably the very next issue that he's still lacking a bunch of performance.. my guess is that the sequential reads arent gonna go up at all.

[Nick7]

RAID5 with Storage Spaces is known for horrid write performance.

However, there is light at the end of the tunnel!

 

Check this page: https://wasteofserver.com/storage-spaces-with-parity-very-slow-writes-solved/

 

It explains how to setup RAID5 in Storage Spaces properly, and with that you can get decent write performance.

I have tested this with 5 drive setup, and it worked almost as fast as with SAS RAID controller in RAID5.

[Jarsky]

19 hours ago, Wauter said:

Crucial BX500 SSD's.

 

I'll point out that those are very cheap SSD's. They use TLC but have no DRAM cache and very limited pseudo SLC cache (they use some of the TLC in SLC mode). 

If that cache gets saturated, the speeds absolutely tank. Opening 50GB VM disk images, is not going to be a great time when they drop to 5MB/s each (~15MB/s max across the array)..

 

If you want to use Crucial, you really at least need the MX500's or better for VM usage.