A couple of posts ago in this series, I explained how a NAND flash die is comprised of planes, which contain blocks, which contain pages… which contain individual cells of data. Read operations take place at the page level, as do write operations (although we call them program operations in the flash world). But crucially, erase operations take place at the block level and so affect multiple pages.
Erases are also (more...)
This is another guest post from my buddy Nate Fuzi, who performs the same role as me for Violin but is based in the US instead of EMEA. Because he’s an American, Nate believes that “football” is played using your hands and that the ball is actually egg-shaped. This is of course ridiculous, because as the entire rest of the world knows, this is football whereas the game Nate is thinking of is (more...)
In my previous post on the subject of the new ASM Filter Driver (AFD) feature introduced in Oracle’s 126.96.36.199 patchset, I installed the AFD to see how it fulfilled its promise that it “filters out all non-Oracle I/Os which could cause accidental overwrites“. However, because I was ten minutes away from my summer vacation at the point of finishing that post, I didn’t actually get round to writing about what (more...)
This is a very quick post, because I’m about to log off and take an extended summer holiday (or vacation as my crazy American friends call it… but then they call football “soccer” too). Before I go, I wanted to document my initial findings with the new ASM Filter Driver feature introduced in this week’s 12.1.o.2 patchset.
Currently a Linux-only feature, the ASM Filter Driver (or AFD) is a replacement for ASMLib (more...)
Vanuit Proact organiseren wij het kennisplatform SYNC 2014 op 17 september in de Rotterdam Cruise Terminal. Alle hedendaagse IT-infrastructuurontwikkelingen in 1 dag:
• Een interactief programma o.l.v. dagvoorzitter Lars Sørensen o.a. bekend van BNR
• Een keynote van Marco Gianotten van Giarte, de Nederlandse “Gartner” op het gebied van Outsoucing/Managed Services
• Huisman Equipment over de
For some time now I have preferred Oracle SLOB as my tool for generating I/O workloads using Oracle databases. I’ve previously blogged some information on how to use SLOB for PIO testing, as well as shared some scripts for running tests and extracting results. I’ve now added a whole new landing page for SLOB and a complete guide to running sustained throughput testing.
Why would you want to run sustained throughput tests? Well, one (more...)
The last post in this series discussed the layout of NAND flash memory chips and the way in which cells can be read and written (programmed) at the page level but have to be erased at the (larger) block level. I finished by mentioning that erase operations take substantially longer than read or program operations… but just how big is the difference?
Knowing the answer to this involves first understanding the different types of flash (more...)
In the last post on this subject I described the invention of NAND flash and the way in which erase operations affect larger areas than write operations. Let’s have a look at this in more detail and see what actually happens. First of all, we need to know our way around the different entities on a flash chip: the die, the plane, the block and the page:
NAND Flash Die Layout (image courtesy (more...)
In the past I have been a little critical of Oracle’s support notes and documentation regarding the use of Advanced Format 4k storage devices. I must now take that back, as my new friends in Oracle ASM Development and Product Management very kindly offered to let me write a new support note, which they have just published on My Oracle Support. It’s only supposed to be high level, but it does confirm that the _DISK_SECTOR_SIZE_OVERRIDE (more...)
It's just under a week to go before the doors open for the UKOUG Tech13 conference and the adjoining OakTable World UK 2013 sessions, so I thought I would write a very short blog post about what I will be doing there, where I'll be, and what I'm looking forward (more...)
In this post I want to show how to test what will happen with your cluster if you simply detach shared storage device from it. VirtualBox is great tool for that purpose because you can test such scenario without involving many people or causing any damage.
I am aware that (more...)
Last week I had a lengthy post at oracle-l that tackles Calibrate IO, Short Stroking, Stripe size, UEK kernel, and ASM redundancy effect on IOPS Exadata which you can read here
followed by interesting exchange of tweets with Kevin Closson here (see 06/21-22 tweets) which I was replying in between games at UnderwaterHockey US Nationals 2012 which we won the championship for the B division I have my awesome photo with the medal here
This post will detail on the ASM redundancy/parity effect on IOPS… if… by changing the ASM redundancy (external, normal, and high) will it decrease the workload (more...)
I was doing some installation at customer site when they asked if there anything specific to run GI 11.2 on HP-UX as this was their first interaction with 11g. Of course I replied that there is nothing specific, just to make sure the ownership of the raw disk is correct and had a correct ASM discovery string. They said that this is all done as it’s written in the documentation, but disks could not be discovered. This made me curious and asked them to log me in the system so I could have a look.
The system was running (more...)
On my post about observing the Exadata V1 I had an interesting comment posted by Mark Seger (author of collectl and collectl utilities) about the correlation of activities across a system, the sample and snap time, and seeing the state of the subsystem before and after…
The comment made me curious about the effect of snap intervals on the performance numbers of the datafiles and block devices.. especially on the latency numbers.. so I made a few test cases and created some scripts that would give me 5 seconds, 10 minutes, and 60 minutes output of (more...)