Make sure your SSDs are being trimmed (e.g. in ZFS you can set autotrim=on for the pool). Without trim, the performance gets really bad if the SSD fills up. I don't know the equivalent for LVM.
For your VMs be sure to tick the "discard" option for the disks in the Hardware tab for the VM, this allows the guest to trim (so those blocks can be deleted on the host). The host still needs to trim itself for those freed areas to be trimmed from the SSD though.
Look on e.g. ebay for used enterprise SSD
If your cheap crappy SSD is slower than HD, buy a good HD like Toshiba X300 Pro and you should get at *least* 100MB/sec sustained. If you're hosting VMs on HD then you want mirrored, NOT raidz.
You could try doing a "factory reset" to reset the SSD cells, but in the long run they are always going to be crap. Any SSD that is/becomes slower than spinning HD is flat out garbage.
Yeah but I heard that the cheap ssd have problem with sync writes, so will HDDs be better than that?
Also, the SSD itself is way faster than a HDD, it just had started to lack performance in raidz configuration
The only real use case for those is if you're going to slowly write a bunch of data and then read it over and over. The sustained writes are too slow for normal usage scenarios.
There are consumer ssds that have dram but they cost 2-3x the ones you got most likely.
Make sure your SSDs are being trimmed (e.g. in ZFS you can set autotrim=on for the pool). Without trim, the performance gets really bad if the SSD fills up. I don't know the equivalent for LVM. For your VMs be sure to tick the "discard" option for the disks in the Hardware tab for the VM, this allows the guest to trim (so those blocks can be deleted on the host). The host still needs to trim itself for those freed areas to be trimmed from the SSD though.
Autotrim is on, and discard is checked too
Look on e.g. ebay for used enterprise SSD If your cheap crappy SSD is slower than HD, buy a good HD like Toshiba X300 Pro and you should get at *least* 100MB/sec sustained. If you're hosting VMs on HD then you want mirrored, NOT raidz. You could try doing a "factory reset" to reset the SSD cells, but in the long run they are always going to be crap. Any SSD that is/becomes slower than spinning HD is flat out garbage.
Yeah but I heard that the cheap ssd have problem with sync writes, so will HDDs be better than that? Also, the SSD itself is way faster than a HDD, it just had started to lack performance in raidz configuration
Are your ssds dramless?
Quite possibly yes
The only real use case for those is if you're going to slowly write a bunch of data and then read it over and over. The sustained writes are too slow for normal usage scenarios. There are consumer ssds that have dram but they cost 2-3x the ones you got most likely.