So, apparently I missed the memo — iOS 4 has IPv6 support. I’ve been wanting IPv6 support for a while and I thought I checked around enough after the iOS 4 announcement, but I didn’t find anything at the time. It turns out it doesn’t take anything extra. With my current setup at home, our iPhones are already on IPv6. After finding out that it should be working I checked and sure enough it is. Magic.
I’ve now been living with an iPhone 4 for a month. I’m sure few would be surprised for me to call it a great smartphone. As I said in my previous post, the screen is the outstanding feature. I am truly amazed at this “Retina display”. I actually carry 2 iPhones (work-issued and personal). My work phone is an iPhone 3GS. So, I’m reading each on a daily basis. When they were both 3GS I was a happy camper (except for having to carry 2 phones). Now, every time I check e-mail on the 3GS I’m reminded how poor the screen is in comparison to the 4. The difference is striking. I’m a gadget freak, so I would have picked up this new version anyway, but the screen itself is totally worth the upgrade. In fact, it almost makes me disappointed in the the iPad 3G, which is nearly as new. I know — totally different beast.
I waited in line to get the iPhone 4 today and came away successful. I don’t yet know if this is a great new phone, but it has an amazing screen. I am blown away by the clarity. It’s like going from an SDTV to an HDTV. Text looks like it’s back-lit print — just amazing.
The purchasing experience was great too. Note that today is the second day of their availability. My working theory was that there would be some reservations that weren’t picked up on day one and those go in the available-to-walk-ins pool. I was sure others would be thinking the same way. I’m not totally nuts, though, so I got in line at 7am (for a scheduled 8am early opening). I was about number 20 in line. I talked to the folks around me and it seems everyone had been there the day before. It sounds like that had been a real zoo. It took about 30 minutes for me to get inside once the doors opened. I spent another 30 minutes getting and activating the 2 I was after. Not too bad. Now what do I do with 2 iPhone 3GS?
So, after a half-day with iOS 4, I have some opinions. Note that I have an iPhone 3GS.
So, I was one of the crazy people that was in line for the iPad 3G’s release at 17:00 yesterday. I had been debating it most of the week and made a last minute decision to go for it. I did a quick check of the Macrumors iPad forum to see how the lines might be and they seemed to be pretty minimal. So, I made a break for it just after 16:00. It took me about 25 minutes to get there, so I didn’t get in line until about 16:30.
At that pint I was probably about 50 back people in line. That caught me by surprise. As we approached 17:00 the line quickly doubled. Demographic make-up was across the board. This product seemed to have a broad appeal. One guy I was standing near already has an iPad and was looking for the extra mobility of the 3G. With so many people in line we were all a bit concerned about availability. Shortly before 17:00 an Apple employee started working down the line surveying us with an iPod Touch. He’d ask us which model we’re looking for and enter it in his little application. After a second or two it would report back if there was availability for that model and he’d move down the line. The 64GB model was available. Yes. We could start to hear cheers of jubilation coming from within the store. What was going on up there?
The line moved pretty quickly and when I got up to the front there were a lot of people coming up to the line-minder asking about availability. He couldn’t reveal inventory levels, but there were a lot of folks concerned they’d wait in line for an hour and go home empty handed. One lady wasn’t even interested in a 3G model, she wanted a plain iPad, but was driving to Hattiesburg next and wanted to know whether or not it would be worth waiting in line or if she should already hit the road. Pretty much everybody in line was after the 3G, so she shouldn’t have much to worry about.
Then my turn came. I was assisted by Helen (one of two Helens, apparently). She took me inside the store and it was obviously all-hands-on-deck. That was a bustling storm of activity. There were people everywhere. Money was flying at Apple. I got one the 64GB models and the dock and was outta there almost exactly at 17:30. As I walked out the staff erupted in cheers — nice touch.
We went to the Apple store today to see/play with the new iPad. Much to my surprise, we had to wait in line to get in the store. Apparently, it was fire code compliance, but I think I’ve seen the store more crowded before. Despite the line, we were inside in under 5 minutes. Then we spent about 15 minutes with a demo unit. In some ways it was like big iPod touch, but the extra screen real estate can be put to great use. I’m primarily looking at it for web surfing and for that purpose it seems to excel. The vocal critics citing a lack of Flash is not something that dissuades me. Having had numerous BSD/Solaris/Linux systems without Flash over the years, it just doesn’t bother me. Maybe I just don’t spend enough time watching embedded videos. I’m hoping this device gives critical mass to HTML5, and the decline of Flash (but I’m not holding my breath). Being that the base OS is shared with the iPhone I thought the Thai support would be the same, but it’s not. Thai does appear to be supported in Safari. I pulled up Thairath and did a bit of browsing. Wow, that’ll be perfect for grandpa. Going into the settings applet there was no Thai option for setting up an additional keyboard like I can on my iPhone. That’s not a dealbreaker, but I hope it returns. So, I’m looking forward to probably picking up the 3G version when they come out later this month.
My big ZFS pool on my SageTV server recently hit 2/3 capacity. It’s amazing just how big HD shows are, and I record a lot of them (probably too many). I needed to do something before I ran out of space, so I ordered 4 more 2TB Hitachi drives. This box doesn’t have hot-swap capability, but if it had I think I could have done this with 1 reboot. So, I pulled out 2 of the 1TB drives from separate mirrored pairs and replaced them with 2 2TB drives. Then I ran ‘zfs replace’ for each missing drive and in about 3 hours it was done resilvering. I did this again for the other 2 1TB drives from those 2 mirrored pairs. A reboot later and my array now shows 5.44TB capacity. It appears throughput has increased as well. So, this is my 3rd capacity expansion on this pool and I think ZFS is indispensable for it. There’s no doubt that 6 hours of resilvering better than having to find some place to back up everything (if I even have that much space anywhere), backing it up, rebuilding the array, and then restoring.
We rented Transformers: Revenge of the Fallen on iTunes last night. Two words: pure crap. I can’t believe they put something this bad out and that it made as much money as it did. Ridiculous.
The devil is always in the details. Software systems can be quite complex and assumptions about how they work can get you in trouble. On my previously mentioned TV server, this week, I noticed some nearly unwatchable shows. My initial thought was that I needed to realign my antenna, but I noticed that the shows were all recorded at the same time and I was watching another. Maybe they were bandwidth starved? The worst stutters were during scenes with lots of motion. Now, in my previous setup, I know I was not able to watch anything while recording 4 HD shows. At least I could record 4 HD show simultaneously. The old setup was only one disk, though. Now I’m running a one disk ZFS RAIDZ. I absolutely know RAID5 type setups don’t perform like RAID0 setups (and that RAIDZ isn’t exactly RAID5), but early generalizations I’d read lead me to expect RAID5 type performance. I didn’t investigate further and made assumptions based on my understanding of the technology. Boy was I wrong. Take a look at the numbers from bonnie++:
Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP dagobah.boonthe 16G 96 99 131609 34 104142 31 277 99 271779 41 116.4 14 Latency 253ms 7136ms 7453ms 36211us 731ms 785ms Version 1.96 ------Sequential Create------ --------Random Create-------- dagobah.boontheekul -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 22615 96 +++++ +++ 17543 97 20137 91 +++++ +++ 18455 98 Latency 12940us 9652us 227us 18233us 153us 377us
Those are crazy numbers. So, I turned to Google and did some more reading. It turns out a RAIDZ’s write performance is much worse than I expected. This quote (well, quote of a quote) is very good:
"Now we come to the crucial decision ZFS has made for raidz and raidz2: in raidz and raidz2, the data block is striped across all of the disks. Instead of a model where a parity stripe is a bunch of data blocks, each with an independent checksum, ZFS stripes a single data block (and its parity), with a single checksum, across all the disks (or as many of them as necessary). This is a rational implementation decision, but when combined with the need to verify checksums, it has an important consequence: in ZFS, reads always involve all disks, because ZFS always must verify the data block's checksum, which requires reading all of the data block, which is spread across all of the drives. This is unlike normal RAID-5 or RAID-6, in which a small enough read will only touch one drive, and means that adding more disks to a ZFS raidz pool does not increase how many random reads you can do per second. (A normal RAID-5 or RAID-6 array has a (theoretical) random read IO capacity equal to the sum of the random IO operations rate of each of the disks in the array, and so adding another disk adds its IOPs per second to your read capacity. A ZFS raidz or raidz2 pool instead has a capacity equal to the slowest disk's IOPs per second, and adding another disk does nothing to help. Effectively a raidz ZFS gives you a single disk's read IOPs per second rate.)" This was on a blog of a SUN engineer (although a post from a few years ago), unfortunately I don't have the link, I actually had to go through my posting history on the Ars Technica forum to even find this quote in the first place. If the situation has changed and the above quote no longer holds true, it would be nice if someone more knowledgeable on the performance implications could elaborate what kind of performance is to be expected on a raidz system- Sincerely, Dan Naumov
Wow. In that same thread and in another I found, someone posted some benchmarking results they had done. They are very interesting. Follow these links:
http://virtual.tehinterweb.net/livejournal/2009-06-22_zfs_diskperf/zfs-diskperf-contig-write.png
http://virtual.tehinterweb.net/livejournal/2009-06-22_zfs_diskperf/zfs-diskperf-5MB-readwrite.png
http://virtual.tehinterweb.net/livejournal/2009-06-22_zfs_diskperf/zfs-diskperf-1MB-readwrite.png
I was quite surprised. Further reading has lead me to rethink my setup. For this TV/media server I need the ability to read and write simultaneously at high rates. Write speed is more important in that I’ll likely be recording more shows at any given time than I’m watching, but I’ll still need to be able to stream a couple of HD shows at the same time. Heck, my 4 tuners haven’t been enough on a couple of occasions. So, I’m going to have to sacrifice space for speed. I don’t know how I’m going to do the data shuffle, but I’m considering picking up another pair of 1TB drives and a PCI-Express SATA controller (only one free one left on the mainboard). That’ll help. Then I guess I’ll build the pool from mirrored pairs of 1TB drives. My read/write performance should improve, but the addition of 2TB more drives won’t give me any more space. It will be interesting to see what kind of numbers I get out of it.
Update: I reconfigured the pool from a 4 disk RAIDZ to a pool of 2 2 disk mirrors. Bonnie++ results:
Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP dagobah.boonthe 16G 89 99 95149 25 87337 23 289 99 270826 31 214.8 28 Latency 354ms 11106ms 10391ms 40391us 3882ms 464ms Version 1.96 ------Sequential Create------ --------Random Create-------- dagobah.boontheekul -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 20303 95 +++++ +++ 8108 99 19027 97 11837 99 4149 99 Latency 13531us 265us 478us 39328us 308us 5922us
Update: I got in 2 more 1TB disks (and a HighPoint 2310, as I’ve used up all 6 on-board SATA ports). I added the 2 new disks (via the HighPoint, no other rearranging of the drives) as another mirror in the pool. Now the capacity is back up to what it was as a RAIDZ. Bonnie++ results:
Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP dagobah.boonthe 16G 112 99 145807 39 124058 33 289 99 372925 46 274.9 22 Latency 331ms 3891ms 7095ms 31678us 2229ms 457ms Version 1.96 ------Sequential Create------ --------Random Create-------- dagobah.boontheekul -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 22492 94 +++++ +++ 19562 97 16765 97 18918 99 6837 99 Latency 18093us 1113us 185us 37416us 203us 386us
It’s hard to make any conclusions from this. The numbers for the pool of mirrors are completely different than what I expected. In addition, I can say that interactive performance with similar workloads to what caused me problems previously have much improved. Just from the reconfiguration of the existing drives, I was able to record 4 HD streams simultaneously while watching another and no apparent stuttering or the like in any recording or the playback. Adding the 2 additional disks as another mirror in the pool had apparent impact in the bonnie++ numbers and brought my usable space back up to previous levels, but I’m still rather surprised at the bonnie++ numbers.
As I’ve mentioned, I’ve been very interested in ZFS lately. Well this week, the hypothetical happened to me and ZFS was there to make it a non-event. I was checking up on my newest ZFS’d filesystem (a pair of 1TB drives in a ZFS mirror). I ran ‘zpool status’ to see how the health of the pool was and it reported that one drive had had a checksum error. I’ve been processing gigs of log files from it, so one block error isn’t much of a pattern. I ran a ‘zpool scrub’ to check everything out (it was clean), and I’ll certainly watch that drive a little closer. ZFS made it simple and seamless.
