Unraid cache drive speed drops to 1-2MB/s under heavy write load

[BOGu]

Hello everyone,

I'm having an issue with my Unraid server and I'm hoping to get some help.

I've added a J.ZAO 3 Series 2.5" 960GB SATA SSD to my array as a cache drive. The drive has been successfully detected, partitioned, formatted, and mounted at /mnt/cache.

The issue I'm having is that when I write a large amount of data to the cache drive, the write speed drops from several hundred MB/s down to 1-2MB/s.

I've checked the SMART information for the drive and there are no errors or warnings. The drive's write cache and read cache are both enabled.

Here is some information that may be relevant to the issue:

 

hdparm -Tt /dev/sde

/dev/sde:
 Timing cached reads:   34382 MB in  1.98 seconds = 17372.10 MB/sec
 Timing buffered disk reads: 576 MB in  3.00 seconds = 191.98 MB/sec

 

iostat output:

05/10/2024 09:37:49 AM
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.75    0.00    0.84   61.89    0.00   36.52

Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sde              0.00      0.00     0.00   0.00    0.00     0.00    6.00   3888.00     0.00   0.00 1430.33   648.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    8.58 100.00

 

Drive logs：

Apr 29 11:02:04 HOME-unRAID kernel: ata4: SATA max UDMA/133 abar m2048@0x87613000 port 0x87613280 irq 130
Apr 29 11:02:04 HOME-unRAID kernel: ata4: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Apr 29 11:02:04 HOME-unRAID kernel: ata4.00: ATA-11: J.ZAO 3 SERIES 2.5 INCH 960GB SATA SSD, SN12155, max UDMA/133
Apr 29 11:02:04 HOME-unRAID kernel: ata4.00: 1875385008 sectors, multi 1: LBA48 NCQ (depth 32), AA
Apr 29 11:02:04 HOME-unRAID kernel: ata4.00: configured for UDMA/133
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] 1875385008 512-byte logical blocks: (960 GB/894 GiB)
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] Write Protect is off
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] Mode Sense: 00 3a 00 00
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] Preferred minimum I/O size 512 bytes
Apr 29 11:02:04 HOME-unRAID kernel: sde: sde1
Apr 29 11:02:04 HOME-unRAID kernel: sd 4:0:0:0: [sde] Attached SCSI disk
Apr 29 11:04:07 HOME-unRAID emhttpd: J.ZAO_3_SERIES_2.5_INCH_960GB_SATA_SSD_NBN380T000280 (sde) 512 1875385008
Apr 29 11:04:07 HOME-unRAID emhttpd: import 30 cache device: (sde) J.ZAO_3_SERIES_2.5_INCH_960GB_SATA_SSD_NBN380T000280
Apr 29 11:04:07 HOME-unRAID emhttpd: read SMART /dev/sde
Apr 29 11:04:16 HOME-unRAID emhttpd: shcmd (42): mount -t xfs -o noatime,nouuid /dev/sde1 /mnt/cache
Apr 29 11:04:16 HOME-unRAID kernel: XFS (sde1): Mounting V5 Filesystem
Apr 29 11:04:16 HOME-unRAID kernel: XFS (sde1): Ending clean mount
May 10 09:27:39 HOME-unRAID kernel: sd 4:0:0:0: [sde] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

 

I've tried searching the Unraid forums for similar issues but haven't been able to find anything that has helped.

Has anyone else experienced a similar issue? Any advice or help would be greatly appreciated.

 

System Information:

Unraid version:6.12.10

Hardware: HPE Microserver GEN10 Plus Server

Cache drive: J.ZAO 3 Series 2.5" 960GB SATA SSD

home-unraid-diagnostics-20240507-1541.zip

[JorgeB]

Looks to me more like a device problem, most SSDs cannot keep up high write speeds, though that's kind of extreme, but I'm not familiar with the brand model, do you have another device you could test with? Ideally a known good performer, like the Samsung 870 EVO or Crucial MX500.