search for: preallocation

Hi All I was reading through this: http://kashyapc.com/2011/12/02/little-more-disk-io-perf-improvement-with-fallocateing-a-qcow2-disk/ I was basically searching for pointers on improving disk I/O. I wanted to know the purpose of preallocation=full & preallocation=metadata , What is the difference between them ? and which one would yield a better disk I/O speed ? Appreciate your responses in this regard. Thanks Jatin

For raw, this allows "off" as a synonym for "sparse" (to make it consistent with qcow2). For qcow2, this allows "sparse" as a synonym for "off". It also adds qcow2 "full" preallocation, which is actually mapped to the qemu option "falloc" (see arguments about this on the qemu-devel mailing list, which we lost). This also updates the test. --- generator/actions.ml | 13 +++++++------ src/create.c | 16 ++++++++++++---- tests/create/test-...

...sk/ In my testing, the above method gives near-raw performance as it preallocated all the space ahead of time. The above test can now be done in a single command -- see option (3) below. > I was basically searching for pointers on improving disk I/O. > > I wanted to know the purpose of preallocation=full & preallocation=metadata > > > , What is the difference between them ? and which one would yield a better > disk I/O speed ? There are three options that modern `qemu-img` supports: (1) 'preallocation=metadata': allocates qcow2 metadata, and it's still a spars...

Hi All, When I tried to create preallocated image with gluster , I am unable to create one The image gets created but not preallocated. [root@ ]# qemu-img create -f qcow2 -o preallocation=full gluster://host1.lab.eng.blr.redhat.com/rep3vol/vm3.img 3G Formatting 'gluster://dhcp37-61.lab.eng.blr.redhat.com/rep3vol/newvm3.img', fmt=qcow2 size=3221225472 encryption=off cluster_size=65536 preallocation='full' Unknown option 'preallocation' Is it a known issue...

Bringing this back up for discussion on handling exceptions. According to the inalloca design <https://llvm.org/docs/InAlloca.html>, there should be a stackrestore after an invoke in both the non-exceptional and exceptional case (that doesn't seem to be happening in some cases as we've seen, but that's beside the point). Does it make sense to model a preallocated call as

I believe that the changes to support --preallocate and --sparse together have broken --preallocate by itself (commit f3873b3d88b61167b106e7b9227a20147f8f6197) The previous behavior of --preallocate was to do just that: reserve blocks in the filesystem WITHOUT setting the size of the file to the final length. The reported filesize would change as the preallocated blocks were actually written.

When creating qcow2 images using virt-builder, is there a way to specify the qcow2 preallocation, as possible with qemu-img create -o preallocation=metada , for example? TIA, Y.

...wrote: > > > On Tue, May 17, 2016 at 03:41:53PM +0100, Richard W.M. Jones wrote: > > > On Tue, May 17, 2016 at 05:15:57PM +0300, Yaniv Kaul wrote: > > > > When creating qcow2 images using virt-builder, is there a way to > > specify > > > > the qcow2 preallocation, as possible with qemu-img create -o > > > > preallocation=metada , for example? > > > > > > No .. but .. it does default to preallocation=metadata provided that > > > the output format is qcow2: > > > > > > > > https://github.com/libgu...

I've read in Phil Spector's new book that it's a good idea to preallocate a big matrix, like u <- matrix(0,nrow,ncol) # (1) Now, I read contents of a huge matrix from a Fortran binary dump. u <- readBin(con,what="double",n=nrow*ncol) # (2) If I do (1) and then (2), u is a vector, obviously it's either reallocated or its matrix nature is lost -- overridden?

On Tue, May 17, 2016 at 03:41:53PM +0100, Richard W.M. Jones wrote: > On Tue, May 17, 2016 at 05:15:57PM +0300, Yaniv Kaul wrote: > > When creating qcow2 images using virt-builder, is there a way to specify > > the qcow2 preallocation, as possible with qemu-img create -o > > preallocation=metada , for example? > > No .. but .. it does default to preallocation=metadata provided that > the output format is qcow2: > > https://github.com/libguestfs/libguestfs/blob/master/builder/builder.ml#L582-L585 I should...

On Sat, Mar 28, 2020 at 2:20 PM Eli Friedman <efriedma at quicinc.com> wrote: > This would specifically be for cases where we try to rewrite the > signature? I would assume we should forbid rewriting the signature of a > call with an operand bundle. And once some optimization drops the bundle > and preallocated marking, to allow such rewriting, the signature doesn’t > need

Hi folks I am trying to install CentOS 5.2 in Vmware Server environment. In my VM disk space is not preallocated for the virtual disk (dynamically). The installer doesn't find the disk. When preallocating 6 GB there is no problem. See screenshot[0] Any ideas? kind regards Sven [0] http://bayimg.com/image/lamidaabe.jpg

...Priority: P5 Component: core AssignedTo: wayned at samba.org ReportedBy: wgordonharris at gmail.com QAContact: rsync-qa at samba.org With rsync version 3.1.0dev protocol version 31.PR14, using the --preallocate and --recursive options: It appears as though preallocation only happens with files in the first directory copied. In subsequent directories, rsync seems to revert to stock behavior, i.e. no preallocation. Command line used: rsync --links --perms --times --group --owner --devices --specials --stats --progress --verbose --preallocate --recursive --include...

Greetings, I would like to write a patch for rsync but need some help getting started. Here is my situation. I am using cwrsync to copy files from one Windows server to another Windows server. One file that I need to backup is 130 GB. The daily changes occur all throughout the file, not just at the end of the file. File names look like this: Db_20080402_0003_DB.BAK Db_20080403_0003_DB.BAK

When I use the preallocate patch and create a 77GB file using the function I get a CPU spike on the server-side. The spike lasts about 20 minutes and uses about 20%-25% of the cpu associated with the rsync instance creating the file. The spike is directly linked to the time it takes to create the file. I compiled rsync using cygwin CVS. I initially suspected the implementation of

...gt; On Tue, May 17, 2016 at 03:41:53PM +0100, Richard W.M. Jones wrote: > > > > On Tue, May 17, 2016 at 05:15:57PM +0300, Yaniv Kaul wrote: > > > > > When creating qcow2 images using virt-builder, is there a way to > > > specify > > > > > the qcow2 preallocation, as possible with qemu-img create -o > > > > > preallocation=metada , for example? > > > > > > > > No .. but .. it does default to preallocation=metadata provided that > > > > the output format is qcow2: > > > > > > > > >...

...sfactory plan. (Even worse because `--output-alloc sparse' is the default!) So then I tried to add `--output-alloc prefer-sparse' as the default. The problem with that is the planner could choose to use a preallocating transition (eg. "cp --sparse=never" or "qemu-img ... -o preallocation=full"), when ideally we'd always want it to choose sparseness if possible. It may be possible to use the planner weights to avoid this, but I'm not convinced the way we handle weights is very robust (in particular, plans with lower total weight but more steps are ignored). Adding som...

Hi Timo, Any chance the mbox/mdbox writer code could be modified to do physical preallocation on files to help avoid file(system) fragmentation? Constantly appending a file is the prime recipe for causing fragmentation, and mbox is notorious for this--not a fault of Dovecot but the nature of the mbox beast. Obviously maildir doesn't have such a problem, but some (many?) of us still pre...

Hello all, A few years ago, I added the inalloca feature to LLVM IR so that Clang could be C++ ABI compatible with MSVC on 32-bit x86. The feature works, but there is room for improvement. I recently took the time to write up a design using token values that will hopefully be better named and easier to work with and around. For the technical details of the proposal, I've written up the RFC

...ship and - * permissions correctly if required. + (* As a special case, allow output to a block device or + * symlink to a block device. In this case we don't + * create/overwrite the block device. (RHBZ#1868690). *) - (* What output preallocation mode should we use? *) - let preallocation = - match t.target_format, cmdline.output_alloc with - | ("raw"|"qcow2"), Sparse -> Some "sparse" - | ("raw"|"qcow2"), Preallocated -> Some "full" -...