Posts Tagged ‘RAID5’
Ask any user of a SAN if cache matter. Cache DOES matter. Cache is King! But apart from being “just” something that can handle your bursty workloads, there is another advantage some vendors offer when you have plenty of cache. It is all in the implementation, but the smarter vendors out there will save you significant overhead when you use RAID5 or RAID6, especially in a write-intensive environment.
Recall on RAID
Flashback to a post way back: Throughput part 2: RAID types and segment sizes. Here you can read all about RAID types and their pros and cons. For now we focus on RAID5 and RAID6: These RAID types are the most space efficient ones, but they have a rather big impact on small random writes. Read the rest of this entry »
In a previous blogpost I covered the general issue of misalignment on a disk segment level. This is the most occurring and the most obvious misalignment, where several spindles in a RAID set perform random I/O and misalignment causes more spindles need to seek for a single I/O than would be required when properly aligned.
Next in the series there is another misalignment issue which is rare, but can have a much bigger impact on tuned storage: Full stripe misalignment.
Is it a new miss election?? Well, after doing more than a little testing I figured out I may be MISSing something… So unfortunately it is not about beautiful women, but yet another technical deepdive. This time into misalignment. Theoretically it is SO easy to point out what the problem is (see Throughput part 3: Data alignment. For this new blog entry I had my mind set on showing the differences between misalignment and alignment in the lab… However this proves to be much MUCH harder than anticipated…
In this post: Throughput part 2: RAID types and segment sizes I wrote that a RAID5 setup can potentially perform better in a heavy-write environment over RAID10, if tunes right. While theoretically this might be true, I have some important addendum’s to this statement that vote against RAID5 which I’d like to share.
In part one I covered all stuff you can think of in regards to delays and latencies you encounter on physical disk drives and solid states. Now it is time to see how we can string together multiple drives in order to get the performance and storage space we actually require. I’ll discuss RAID types, number of disks in such a RAID set, segment sizes to optimize your storage for particular needs and so on.
–> For those of you who haven’t read part 1 yet: Thoughput Part1: The Basics
A short intro to RAID types
Now finally it is on to the stringing together of disks. More disks is more space, more performance, right? Yes right – sometimes. I am not zooming in too deep on the RAID types. I assume you have some knowledge on different types of RAID, mainly RAID1, RAID10 and RAID5. All that I’ll say about it: Read the rest of this entry »