Does anyone know if an openSUSE installation from scratch properly aligns partitions on an SSD (similar as to how an installation from scratch with Windows 7 does) ?
Out of ignorance to the matter, I initially cloned an existing 11.3 installation from an older mechanical hdd to the sdd (a 60gb sandforce drive). After being not overly impressed with the difference in performance between the ssd and the older hdd, I began to investigate and soon afterwards learned about the alignment issue.
I’ve since then tried a few things, but I’m not certain if I’ve managed to get the partitions properly aligned to the block, and rather suspect that they aren’t.
To be sure, there are some definite performance improvements in some areas over the older hdd, but, in general, it (the performance gain) was hardly worth the money for the ssd, let alone the drop down in storage capacity. In addition, having to learn about alignment issue and secure erase turned out to be a time consuming PITA. And it doesn’t end, cause, while I’m now clear on how to properly set up a single partition under Windows, I’m not at all sure about the likes of under Linux, and its typical multi-partition setup (swap, root, home). There isn’t a whole lot of Linux based info to go on (I’ve collected some links, but admit that I have yet to thoroughly go through them, owing to a general lack of time, as well as a current lack in interest of devoting more time delving deeper into this an arcane aspect of SSDs that I initially had no clue about).
I’m hoping its just a misconfiguration issue, and that I can generate a much more noticeable (perceptual, not some silly synthetic benchmark) increase in performance. If that’s not the case, and I’m already running full tilt, then colour me unimpressed. As it is, had I known beforehand about the hassle of alignment, I probably would have forgone the “upgrade” and stuck with an hdd until the software side caught up and was more user friendly PnP in regards to SSDs.
I am no expert on SSD, but here is an interesting stuff I have found, Don’t let the Link title fool you. The message is called** Partition alignment in Linux**:
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ADJUSTING PAGE TRIMMING BEHAVIOR
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NOMMU mmap automatically rounds up to the nearest power-of-2 number of pages
when performing an allocation. This can have adverse effects on memory
fragmentation, and as such, is left configurable. The default behaviour is to
aggressively trim allocations and discard any excess pages back in to the page
allocator. In order to retain finer-grained control over fragmentation, this
behaviour can either be disabled completely, or bumped up to a higher page
watermark where trimming begins.
Page trimming behaviour is configurable via the sysctl `vm.nr_trim_pages'.
**NOMMU_INITIAL_TRIM_EXCESS**
**Turn on mmap() excess space trimming before booting**
The NOMMU mmap() frequently needs to allocate large contiguous chunks of memory
on which to store mappings, but it can only ask the system allocator for chunks in
2^N*PAGE_SIZE amounts - which is frequently more than it requires. To deal with
this, mmap() is able to trim off the excess and return it to the allocator. If trimming is
enabled, the excess is trimmed off and returned to the system allocator, which can
cause extra fragmentation, particularly if there are a lot of transient processes. If
trimming is disabled, the excess is kept, but not used, which for long-term mappings
means that the space is wasted. Trimming can be dynamically controlled through a
sysctl option (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
excess pages there must be before trimming should occur, or zero if no trimming is to
occur. This option specifies the initial value of this option. The default of 1 says that
all excess pages should be trimmed. See Documentation/nommu-mmap.txt for more
information.