Unsolved
1 Rookie
•
35 Posts
0
15
R730xd Atrocious Disk I/O
hey there,
i have this bizarre situation where on an R730xd running an H730 mini, any disk not managed by the perc has just terrible throughput. this includes disk marked as pass-through (non-raid) by the controller, disks attached to the rear bay that the raid controller doens't even see, and usb disks attached using a usb>sata adapter, and both enterprise and consumer drives.
the bandwidth i'm speaking of is, samsung 860 PRO SSD's will cap out at about 80 MB/s sequencial write, and Dell 12k SAS drives will cap out at 50 MB/s.
as soon as i put them behind the perc, then poof! they're dishing out 450 MB/s no issue.
i have also tried putting the controller in HBA mode, no change.
what the heck could be the deal. i have spent all day trying all kinds of scenarios; not an iota of flex.
everything is on the latest firmware, as per connecting to the dell repository in lifecycle controller and checking.
any help here would be appreciated. the goal is the have the controller serve as an HBA so that i can run ZFS on this server. and ZFS does not seem to be causing the issue, because i have also checked other file systems on the disks, and they do equally poorly or worse.
DELL-Erman O
Moderator
Moderator
•
2.5K Posts
0
September 3rd, 2024 09:29
Hello,
First, if the 860 Pro doesn’t have a Dell label, it isn’t Dell-certified. It seems like you’re experiencing an I/O bottleneck when using disks outside of the PERC H730 mini RAID controller on your Dell R730xd server. PCIe slot configurations can sometimes cause bottlenecks, especially if multiple controllers or high-bandwidth devices share the same bus. So please check expansion card installation guidelines to ensure the correct config.
https://dell.to/4cOPN1W
Hope that helps!
jwsl224
1 Rookie
1 Rookie
•
35 Posts
0
September 3rd, 2024 13:20
@DELL-Erman O hey Erman,
the raid controller, the H730 mini, is in a dedicated slot, not PCIe. also, as i mentioned, when i change the attached disks to Raid Mode, they blaze away. when i change them to Non-Raid Mode, they fall around 60 MB/s, dell certified or not. the 12 Gb SAS drives are dell labeled drives and they do the same thing.
DELL-Erman O
Moderator
Moderator
•
2.5K Posts
0
September 3rd, 2024 14:24
Just brainstroming, when you’re not using RAID mode or have drives set up as pass-through, the controller skips the fancy optimizations. It usually falls back to a basic, slower I/O path that doesn’t take advantage of caching or acceleration. In RAID mode, though, the controller uses its cache (like write-back or write-through caching) to speed up I/O operations, making data transfer much faster. But in non-RAID mode, especially with pass-through, the controller might not use its cache well, or at all. This can slow things down since every I/O operation goes straight to the disk without the boost from caching.
jwsl224
1 Rookie
1 Rookie
•
35 Posts
0
September 3rd, 2024 15:08
@DELL-Erman O that part would be plenty fine, as ZFS will use system RAM as cache. but slowing the disks down all the way to 60 MB/s is unusable, even with caching.
to further brainstorm, i installed an HBA330 mini and faced the same issue. the disk performance was abysmal compared to using raid mode.