thomasjcf21
Dabbler
- Joined
- Jun 19, 2019
- Messages
- 15
Hi Everyone,
I'm a new person to the forums, however, before posting this thread I have done a lot of research and gathered lots of information so I just wanted to make sure that my understanding of the information is correct and if not if you could please kindly point me in the right direction.
So firstly I will be using FreeNAS to provide iSCSI backed datastore's to 4 ESXi hosts running around 30 VMs. They'll be more in the future but probably less than 100 for a considerable amount of time. I'm using this for a home environment and mainly a bit of fun, but it also provides services for my family like there offsite backup server etc. So although there is a small amount of important(ish) data there isn't much.
The hardware of the box I wanted to run FreeNAS on is:
Currently there's around a 2:1 L2ARC:ARC ratio which is below the recommended maximum of 4/5:1. Having said that this system has a lot more cache so I was hoping that I wouldn't need to get too much of L2ARC straight away because it should in theory take a while for it all to fill up.
I understand that when creating a iSCSI Target FreeNAS by default sets sync=disabled, which is bad, because when ESXi requests the data to be written to disk (which it does for all requests as it cannot determine the importance of the information) it instead gets written to RAM. Although this is faster it means that if the system was to crash or lock out then all pending writes which haven't been flushed would be lost. This would inevitably result to VM corruption which may not be noticed straight away.
However, the way to mitigate this is to set sync=always which means you MUST have a decent SLOG as without one performance will tank. Having looked online there are a lot of recommendations to get NVMe based devices as they have much lower latency due to the lack of having to serialise and deserialise when communicating to the physical device. The most recommended device is Intel Optane 900P 280GB (£300) or Zeus RAM (£300~). Obviously the size doesn't matter as much as you'll only really assign 8/10GB usable of that drive so that it can do inbuilt drive wear down.
My question is, is there any cheaper SLOG devices which we know can support network speeds of 10GB and also don't have much of an impact on sync=always. Or as this device is UPS backed is it reasonable to accept the risk that the OS may one day crash but this isn't likely and to leave sync=disabled and not invest? After all it's a home system and isn't mission critical data.
Finally with L2ARC the recommendation (as far as I'm aware) is to use NVMe drives when using Networking Speeds of 10GBs otherwise it'll bottleneck your system. Is anyone able to confirm if this finding is true or if standard SATA SSD drives should be ok? If not, are you able to advise any decent (relatively cheap NVMe drives)? I assume a M.2 on a NVMe to PCIe device (4 lanes or x4) might be ok?
Overall I'm new to FreeNAS and after reading Cyberjock's powerpoint presentation I don't want to become another statistic, and I want to make sure that my system can comfortably run FreeNAS without their being lag to my VMs.
So yeah TLDR can anyone advise of any problems that I might have with the above system and as to if they/what SLOG & L2ARC they recommend.
Many Thanks,
Tom.
I'm a new person to the forums, however, before posting this thread I have done a lot of research and gathered lots of information so I just wanted to make sure that my understanding of the information is correct and if not if you could please kindly point me in the right direction.
So firstly I will be using FreeNAS to provide iSCSI backed datastore's to 4 ESXi hosts running around 30 VMs. They'll be more in the future but probably less than 100 for a considerable amount of time. I'm using this for a home environment and mainly a bit of fun, but it also provides services for my family like there offsite backup server etc. So although there is a small amount of important(ish) data there isn't much.
The hardware of the box I wanted to run FreeNAS on is:
- Dell PowerEdge R510 (12x LFF Chassis)
- 128GB ECC DDR3 Memory
- 2x Intel Xeon X5650 @ 2.66 GHz
- Dell H310 (Configured in IT Mode)
- L2ARC - PNY CS900 240GB
- 12 x 2TB 7200 RPM SAS Drives (HP Certified) (soon to change to 12 x 3TB 7200 RPM SATA Drives)
- 2 x 1GB Uplinks Broadcom (soon to change to 10GB SFP+ Uplinks)
Currently there's around a 2:1 L2ARC:ARC ratio which is below the recommended maximum of 4/5:1. Having said that this system has a lot more cache so I was hoping that I wouldn't need to get too much of L2ARC straight away because it should in theory take a while for it all to fill up.
I understand that when creating a iSCSI Target FreeNAS by default sets sync=disabled, which is bad, because when ESXi requests the data to be written to disk (which it does for all requests as it cannot determine the importance of the information) it instead gets written to RAM. Although this is faster it means that if the system was to crash or lock out then all pending writes which haven't been flushed would be lost. This would inevitably result to VM corruption which may not be noticed straight away.
However, the way to mitigate this is to set sync=always which means you MUST have a decent SLOG as without one performance will tank. Having looked online there are a lot of recommendations to get NVMe based devices as they have much lower latency due to the lack of having to serialise and deserialise when communicating to the physical device. The most recommended device is Intel Optane 900P 280GB (£300) or Zeus RAM (£300~). Obviously the size doesn't matter as much as you'll only really assign 8/10GB usable of that drive so that it can do inbuilt drive wear down.
My question is, is there any cheaper SLOG devices which we know can support network speeds of 10GB and also don't have much of an impact on sync=always. Or as this device is UPS backed is it reasonable to accept the risk that the OS may one day crash but this isn't likely and to leave sync=disabled and not invest? After all it's a home system and isn't mission critical data.
Finally with L2ARC the recommendation (as far as I'm aware) is to use NVMe drives when using Networking Speeds of 10GBs otherwise it'll bottleneck your system. Is anyone able to confirm if this finding is true or if standard SATA SSD drives should be ok? If not, are you able to advise any decent (relatively cheap NVMe drives)? I assume a M.2 on a NVMe to PCIe device (4 lanes or x4) might be ok?
Overall I'm new to FreeNAS and after reading Cyberjock's powerpoint presentation I don't want to become another statistic, and I want to make sure that my system can comfortably run FreeNAS without their being lag to my VMs.
So yeah TLDR can anyone advise of any problems that I might have with the above system and as to if they/what SLOG & L2ARC they recommend.
Many Thanks,
Tom.