20151201

Tue Dec 1 06:18:01 EST 2015 Holy, crap. December. Fugit inreparabile tempus. I went to bed around nine last night, and woke up around six. I slept very well. I don't think I even stirred to take a sip of water from the glass on my nightstand. Rainy with a high of forty-nine today. Goals: Work: - Work on HZ network map, notes Done. - Talk to Jason about HZ No. I have to decide one or two more things before I talk to him. Went for a ten minute walk at lunch (ran short of time to take a longer one). Rainy, but not cold. Home: - Shop at Target Done. - Change sheets and towels Done. - Work on/plan personal server Done. Mounted hard drives in case, and did some planning (see below). Still waiting for motherboard, cpu, ram, and power supply. I should have all my parts by Thursday. Still really digging cwm. It's totally different than wmii, but I like it maybe just as much. Worked on a few C notes. http://constantin.glez.de/blog/2011/02/frequently-asked-questions-about-flash-memory-ssds-and-zfs#both How much space do I need for a ZIL? The role of the ZIL is to store a transaction group until it has safely been written to disk. After that, this can be safely deleted and the space used for the next transaction group. So the question becomes: How much transaction group data is "in flight" (i.e. not yet written to disk) at any time? ZFS issues a new transaction group (and consequently a new pool update) every 5 seconds at the latest (more if the load is higher). While one transaction group is written to the ZIL, the previous one may still be in the process of being written to disk, so we need enough space to store two transaction groups, which means 10 seconds of maximum write throughput worth of data. What's the maximum amount of data that your server writes in 10 seconds? Well, an upper boundary would be the maximum write speed of your SSD. At the time of this writing this was about 170 MB/s for an Intel X25-E, times 10 that would be just short of 2 GB for a typical ZIL. So for ZILs, a little can go a long way. How much space do I need for an L2ARC? This is more difficult, or more easy, depending on how you put it. More is always better, but too much would be a waste if it's not used. Check your L2ARC usage with arc_summary and if you still see a significant amount of ghosts after adding an L2ARC, you'll likely benefit from even more L2ARC space. Another way to estimate L2ARC need is by looking at your working set: The amount of data that is used most frequently. Depending on your application, this could be your top 10 research projects, your top 20% of recurring customers, your most popular 100 products etc. The plan: - Physical disks: - Two 1 TB spinning disks - Three 120 GB SSDs - ZFS use: - Two 1 TB disks as a zfs mirror, used for pure storage, nfs export - Two SSD's: - 400 MB FAT32 partition for UEFI ESP boot on both drives - 10 GB zfs mirror for ZIL cache - Remainder as zfs mirror +100 GB partition for OS filesystems - One SSD dedicated to L2ARC I wrote a FreeBSD 10.2 install image to my USB stick.

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