[SOLVED] SSD performance issue on ext4

[9bitbyte]

Hi All,

I installed proxmox (using ext4 filesystem) on a 5212MB SATA SSD (used consumer-grade Sandisk SD8SB8U512G1001) to evaluate it. I run some benchmarks using fio, to get an idea of how fast it is. Before installing proxmox, I benchmarked the disk with PassMark's Performance Test on Win1o Pro and got tremendously higher sequential writes (around 450 MBps), random r+w and a little bit higher reads.

Should I be troubled with the results? Are these considered normal with proxmox and ext4 ? I wanted to use this as the boot/os disk.

	4KB block size (MBps)	32KB block size (MBps)	1MB block size (MBps)
Random write	38	134	256
Random read	381	530	466
Random read & write (rw)	read=24 / write=24	read=87 / write=87	read=154 / write=162

FYI, fio parameters I used: fio --ioengine=libaio --direct=1 --sync=1 --rw=xxx --bs=4KB/32KB/1MB --numjobs=1 --iodepth=64 --size=4GB --gtod_reduce=1

 

[Dunuin]

If you want comparable result use the same benchmark tool everywhere because otherwise you can't compare numbers. Your fio command for example is doing slow sync writes and I guess your passmark benchmark did fast async writes. If you want to know if ext4 is slow let fio do blocklevel writes directly to the SSD (that destroys everything on the SSD!) and after that partition and format it with ext4 and do the same test on file level.

And if you also plan to run VMs of that OS disk I would use LVM-thin and not plain ext4 so you can store VM images on block level.

 

[9bitbyte]

Thanks for poining me to the right direction! You are absolutely right, I did some diggin' and the standard passmark benchmark (part of it at least), uses uncached async sequential reads and writes with block size of 16K and IO depth of 20. I couldn't use passmark on linux because their suite for linux doesn't include disk benchmarks, unlike the win10 version...

I re-run fio and got the following results on proxmox/ext4, which are indeed closer to what I got from passmark on Win10.

	4KB bs (MBps)	16KB bs (MBps)	32KB bs (MBps)	128KB bs (MBps)	1MB bs (MBps)
Sequential write-Async	244​	419​	483​	415​	313​
Sequential read-Async	245​	484​	507​	496​	485​

To test, I will indeed run the VMs off that disk. The installer by default created volume "data" next to the ext4 root, which uses LVM-thin, and is used to store VM images. Is that what you meant?

Later I was thinking of using this drive just to boot the OS and store the VM ISOs; and run VMs from other SATA HDDs (my current thinking was on ZFS).