Latest interface: 0.3.1
Latest system: 010
Ryan
User

1 posts

Posted on 7 January 2011 @ 00:30
What is the ideal way to set up a Server? Can we entertain a general discussion on an ideal setup?

Here are some questions I would like to see answered as a ZFS newbie (any additional Q/A's would be great):
Will I see performance gains if I install the OS to a SSD?
Will I see a performance hit if I run from a thumb drive?
If I run ZFS on root, are there any draw backs?
Would it be better to run the OS on an AHCI mirror supported by the MB?
Is it better to have the OS installed the SAS/SATA controller cards or the on board SATA?
Is it worth mirroring th OS drive?
How many drives can you put in a RaidZ array before you should consider going to RaidZ2?
Jason
Developer

806 posts

Posted on 9 January 2011 @ 01:43edited 01:45 05s
Will I see performance gains if I install the OS to a SSD?
No, while Windows is crawling with processes that do all sorts of things, FreeBSD system would really be idle most of the time. And even if there were I/O, it shouldn't affect the speeds you receive on your ZFS storage pool which you are accessing from the network.

Rather, install the system to your HDD pool where it receives redundancy (RAID-Z/2/mirror) protection just like your regular files. That leaves your SSDs free for primary storage (create a pool on your SSDs), as L2ARC or cache device or as SLOG/ZIL device.

L2ARC will enhance random read performance, and can be incredibly powerful feature since it allows you to combine 5400rpm HDD and SSD and get the best of both worlds: high sequential I/O and high random reads.

To also enhance random writes and writes in general, using a dedicated "SLOG" aka ZIL device would be an option. However, this option comes with certain danger. If you lose your ZIL device, you could lose your whole pool. This issue was fixed in ZFS pool version 19, but is not part of the stable ZFS releases yet. That's why some recommend to mirror the SLOG, but that's not very sexy. I would wait with SLOG until you have ZFS pool version 19 and SSD with supercapacitor; very important! Intel G3, Sandforce SF2000/2500 and Micron C400 would all have supercapacitor but the current second generation SSDs do not and as such should NOT BE USED for SLOG/ZIL!

You can use any SSD, even USB pendrives or compactflash for L2ARC though, this feature is extremely safe and no risk at all, even if your SSD corrupts data. So primary storage + L2ARC would be the things you can do with an SSD right now.


Will I see a performance hit if I run from a thumb drive or on my primary pool?
No.


If I run ZFS on root, are there any draw backs?
No. More the other way around: the LiveCD uses 600MB of memory extra for memory filesystem. And other FreeBSD systems that use a normal UFS partition for booting, would mean they run a hybrid UFS+ZFS system. Under FreeBSD 8.x, this means that UFS steals memory away from ZFS and not give back to ZFS. This is very inconvenient, and that's why i would recommend a ZFS-only system; exactly what the Root-on-ZFS installation feature gives you.


If i may rephrase your question, which i think you meant:
How bad is losing the system drive; do i need to mirror it?
Losing the ZFSguru system drive should NOT be a bad thing! The worst that can happen is that you need to spend time on reinstalling a new ZFSguru system USB stick and reconfigure your Samba shares and such. Your data on the ZFS pools will not be harmed as a result of losing your system disk.

So don't be afraid to lose it! Just use a simple USB pendrive of 1GB; install Root-on-ZFS on that USB stick; simple! Now to make recovering from failure more easy, you can backup your Samba configuration and such. I plan on adding this feature to the Web-Interface in next release. Then you can export & import your configuration from backup.

Mirroring the system disk shouldn't be necessary also. Either use a USB stick or install to your main ZFS pool so it has some redundancy. The drawback of installing to your primary storage pool, is that you cannot use the Sectorsize override feature; that would render your pool unbootable, for the moment.


How many drives can you put in a RaidZ array before you should consider going to RaidZ2?
For 512-byte sector disks (all older disks):
RAID-Z: between 3 and 6 (tested; verified)
RAID-Z2: between 6 and 10 (tested; verified)
RAID-Z3: between 7 and 11 (not tested; theory only)

Particularly, RAID-Z2 should not be used with 5 disks or below since its performance would be significantly decreased, for some unknown reason. This happened on both 512-byte and 4K-sector disks.

Remember: you can make multiple RAID-Z's. Consider adding disks in groups of 5 disks in RAID-Z or 6 disks in RAID-Z2, for example. This scales better than having 10+ disks in a single RAID-Z.

Also remember: you can use the benchmarking feature on Disks->Benchmark when running in Advanced Mode. This would give you an idea what the optimal configuration is for your hardware. You should perform a Root-on-ZFS installation with memory tuning before you initiate benchmarking.
Jhone
User

16 posts

Posted on 19 February 2019 @ 16:33edited 16:36 05s
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