This doesn't actually relate to the blocksize issue, but a caveat - I've heard that these "green" drives are not suitable for use in a RAID. The specific issue is apparently that these drives spin down very frequently, but most RAID implementations keep spinning them back up again just as frequently (perhaps unnecessarily?), thus causing undue wear and tear on the drives' mechanics and ultimately premature failure. Of course this could be spin from the vendors to get people to spend more money on the "enterprise" level drives - I personally am a firm believer in saving money by buying consumer-level hardware and using the savings to buy extra redundancy. It just so happens that I've bought a batch of Samsung 2TB drives for a RAID6 I'm building, and it turns out they are quite similar to the WDEARS, both in their use of "new format" 4K blocks and some of the green features. I haven't yet detected any undue drive stopping/starting, but then again they are so quite I'm not sure how to check. . . Confirmation or refutation of these thoughts would be most welcome. On Tue, Dec 28, 2010 at 3:46 PM, D.S. Ljungmark <spider@xxxxxxxxxx> wrote: > 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 > -- 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
