The OCZ Vector 180 (240GB, 480GB & 960GB) SSD Review
by Kristian Vättö on March 24, 2015 2:00 PM EST- Posted in
- Storage
- SSDs
- OCZ
- Barefoot 3
- Vector 180
Mixed Random Read/Write Performance
Mixed read/write tests are also a new addition to our test suite. In real world applications a significant portion of workloads are mixed, meaning that there are both read and write IOs. Our Storage Bench benchmarks already illustrate mixed workloads by being based on actual real world IO traces, but until now we haven't had a proper synthetic way to measure mixed performance.
The benchmark is divided into two tests. The first one tests mixed performance with 4KB random IOs at six different read/write distributions starting at 100% reads and adding 20% of writes in each phase. Because we are dealing with a mixed workload that contains reads, the drive is first filled with 128KB sequential data to ensure valid results. Similarly, because the IO pattern is random, I've limited the LBA span to 16GB to ensure that the results aren't affected by IO consistency. The queue depth of the 4KB random test is three.
Again, for the sake of readability, I provide both an average based bar graph as well as a line graph with the full data on it. The bar graph represents an average of all six read/write distribution data rates for quick comparison, whereas the line graph includes a separate data point for each tested distribution.
The Vector 180 does better in mixed 4KB random IO than the 850 Pro, but it's a bit slower than the rest of the drives.
Fortunately the power consumption is still excellent.
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Vector 180's problem is its low random read performance because the performance gets better as more writes are thrown into the mix.
Mixed Sequential Read/Write Performance
The sequential mixed workload tests are also tested with a full drive, but I've not limited the LBA range as that's not needed with sequential data patterns. The queue depth for the tests is one.
In mixed sequential tests the Vector 180 does slightly better in the sense that the difference between drives in the order of 10% when excluding the 850 Pro.
Similar to what we saw in the sequential tests, the write power consumption is fairly high, which also increases the average power consumption and the Vector 180 no longer enjoys an advantage over the other drives.
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Vector 180's "bathtub" curve is pretty average, but as we can see here the power scales as soon as the portion of writes is increased, which isn't unique but for instance the 850 Pro and Extreme Pro don't exhibit such behavior.
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nathanddrews - Tuesday, March 24, 2015 - link
This exactly. LOLSamus - Wednesday, March 25, 2015 - link
Isn't it a crime to put Samsung and support in the same sentence? That companies Achilles heal is complete lack of support. Look at all the people with GalaxyS3's and smart tv's that were left out to dry the moment next gen models came out. And on a polarizingly opposite end of the spectrum is Apple who still supports the nearly 4 year old iPhone 4S. I'm no Apple fan but that is commendable and something all companies should pay attention too. Customer support pays off.Oxford Guy - Wednesday, March 25, 2015 - link
Apple did a shit job with the white Core Duo iMacs which all develop bad pixel lines. We had fourteen in a lab and all of them developed the problem. Apple also dropped the ball on people with the 8600 GT and similar Nvidia GPUs in their Macbook Pros by refusing to replace the defective GPUs with anything other than new defective GPUs. Both, as far as I know, caused class-action lawsuits.Oxford Guy - Wednesday, March 25, 2015 - link
I forgot to mention that not only did Apple not actually fix the problem with those bad GPUs, customers would have to jump through a bunch of hoops like bringing their machines to an Apple Store so someone there could decide if they qualify or not for a replacement defective GPU.matt.vanmater - Tuesday, March 24, 2015 - link
I am curious, does the drive return a write IO as complete as soon as it is stored in the DRAM?If so, this drive could be fantastic to use as a ZFS ZIL.
Think of it this way: you partition it so the size does not exceed the DRAM size (e.g. 512MB), and use that partition as ZIL. The small partition size guarantees that any writes to the drive fit in DRAM, and the PFM guarantees there is no loss. This is similar in concept to short-stroking hard drives with a spinning platter.
For those of you that don't know, ZFS performance is significantly enhanced by the existence of a ZIL device with very low latency (and DRAM on board this drive should fit that bill). A fast ZIL is particularly important for people who use NFS as a datastore for VMWare. This is because VMWare forces NFS to Sync write IOs, even if your ZFS config is to not require sync. This device may or may not perform as well as a DDRDRIVE (ddrdrive.com) but it comes in at about 1/20th the price so it is a very promising idea!
ocztosh -- has your team considered the use of this device as a ZFS array ZIL device like i describe above?
Kristian Vättö - Tuesday, March 24, 2015 - link
PFM+ is limited to protecting the NAND mapping table, so any user data will still be lost in case of a sudden power loss. Hence the Vector 180 isn't really suitable for the scenario you described.matt.vanmater - Wednesday, March 25, 2015 - link
OK good to know. To be honest though, what matters more in this scenario (for me) is if the device returns a write io as successful immediately when it is stored in DRAM, or if it waits until it is stored in flash.As nils_ mentions below, a UPS is another way of partially mitigating a power failure. In my case, the battery backup is a nice to have rather than a must have.
matt.vanmater - Tuesday, March 24, 2015 - link
One minor addition... OCZ was clearly thinking about ZFS ZIL devices when they announced prototype devices called "Aeon" about 2 years ago. They even blogged about this use case:http://eblog.ocz.com/ssd-powered-clouds-times-chan...
Unfortunately OCZ never brought these drives to market (I wish they did!) so we're stuck waiting for a consumer DRAM device that isn't 10+ year old technology or $2k+ in price tag.
nils_ - Wednesday, March 25, 2015 - link
Something like the PMC Flashtec devices? Those are boards with 4-16GiB of DRAM backed by the same size of flash chips and capacitors with a NVMe interface. If the system loses power the DRAM is flushed to flash and restored when the power is back on. This is great for things like ZIL, Journals, doublewrite buffer (like in MySQL/MariaDB), ceph journals etc..And before it comes up, a UPS can fail too (I've seen it happen more often than I'd like to count).
matt.vanmater - Wednesday, March 25, 2015 - link
I saw those PMC Flashtec devices as well and they look promising, but I don't see any for sale yet. Hopefully they don't become vaporware like OCZ Aeon drives.Also, in my opinion I prefer a SATAIII or SAS interface over PCI-e, because (in theory) a SATA/SAS device will work in almost any motherboard on any Operating System without special drivers, whereas PCI-e devices will need special device drivers for each OS. Obviously, waiting for drivers to be created limits which systems a device can be used in.
True PCI-e will definitely have greater throughput than SATA/SAS, but the ZFS ZIL use case needs very low latency and NOT necessarily high throughput. I haven't seen any data indicating that PCI-e is any better/worse on IO latency than SATA/SAS.