Thankyou, This makes planning ahead a bit easier, and means that I "only" have to worry about the traditional issues regarding block sizes, stripe and stride on "naked" disks in the array. Regards, Spid On Mon, 2010-12-27 at 10:59 -0800, Doug Dumitru wrote: > Mr. Ljungmark, > > The meta data is stored at the end of each raid device. So if you are > dealing with an "advanced partitioned" device, just make sure your > individual elements are stores with alignments that make sense. Normally, > this is just 'fdisk -u' and start the partition on a multiple of 8 sectors > (start at 64). > > In terms of stripe sizes, they are all multiples of 4K pages anyway, so it > is not really possible for them to be "wrong" in terms of drive format > alignment. > > File systems should be 4K or multiples thereof. It has been a while, but I > think only XFS really breaks this rule unless you overwrite the block size > to 4K. extn is fine. > > The same rules apply to most SSDs. Most SSDs prefer 4K alignment because of > how the FTL (Flash Translation Layers) operate, even though <4K will > sometimes still work pretty well. > > Doug Dumitru > CTO EasyCo LLC > > On Mon, Dec 27, 2010 at 4:00 AM, D.S. Ljungmark <spider@xxxxxxxxxx> wrote: > > > Hello, > > With the advent of the WD*EARS drives and the "advanced partitioning" > > system that requires 4k blocks, I wanted to pop a quick question to see > > how the md metadata is aligned and how it should be aligned to get > > proper performance out of the devices. > > > > So, For raid1, I'll assume there is some metadata-overhead on the > > drives, how large is this block? Will there be need to make a partition > > on the md-device in order to get proper alignment of filesystem => > > platters? > > > > for both raid1 and 5/6 levels, what are the appropiate stride-sizes for > > ext3/4? > > > > For more advanced raid configurations (5-6), how should the ext3/4 > > stripe size be configured? > > > > > > Yes, a lot of similarly naive questions, however, I'm asking mostly > > because of how devices are changing from 512 to 4k sized blocks, with > > quite interesting changes in performance, and I wanted to figure out > > what is the current state of software raid. At which "level" of the > > stack: (partition) raid (partition) filesystem , do you have to account > > for the block sizes in order to not degrade performance of the devices. > > > > ( In a perfect world I'd be able to purchase a stack of the devices and > > test for myself and come back with a report. However, money and hardware > > is a scarce resource ;) > > > > ps. please keep me CC'd as I'm not subscribed to the list. > > > > > > // Spider > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
