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Diffstat (limited to 'Feature Planning/GlusterFS 3.5/Zerofill.md')
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diff --git a/Feature Planning/GlusterFS 3.5/Zerofill.md b/Feature Planning/GlusterFS 3.5/Zerofill.md deleted file mode 100644 index 43b279d..0000000 --- a/Feature Planning/GlusterFS 3.5/Zerofill.md +++ /dev/null @@ -1,192 +0,0 @@ -Feature -------- - -zerofill API for GlusterFS - -Summary -------- - -zerofill() API would allow creation of pre-allocated and zeroed-out -files on GlusterFS volumes by offloading the zeroing part to server -and/or storage (storage offloads use SCSI WRITESAME). - -Owners ------- - -Bharata B Rao -M. Mohankumar - -Current status --------------- - -Patch on gerrit: <http://review.gluster.org/5327> - -Detailed Description --------------------- - -Add support for a new ZEROFILL fop. Zerofill writes zeroes to a file in -the specified range. This fop will be useful when a whole file needs to -be initialized with zero (could be useful for zero filled VM disk image -provisioning or during scrubbing of VM disk images). - -Client/application can issue this FOP for zeroing out. Gluster server -will zero out required range of bytes ie server offloaded zeroing. In -the absence of this fop, client/application has to repetitively issue -write (zero) fop to the server, which is very inefficient method because -of the overheads involved in RPC calls and acknowledgements. - -WRITESAME is a SCSI T10 command that takes a block of data as input and -writes the same data to other blocks and this write is handled -completely within the storage and hence is known as offload . Linux ,now -has support for SCSI WRITESAME command which is exposed to the user in -the form of BLKZEROOUT ioctl. BD Xlator can exploit BLKZEROOUT ioctl to -implement this fop. Thus zeroing out operations can be completely -offloaded to the storage device , making it highly efficient. - -The fop takes two arguments offset and size. It zeroes out 'size' number -of bytes in an opened file starting from 'offset' position. - -Benefit to GlusterFS --------------------- - -Benefits GlusterFS in virtualization by providing the ability to quickly -create pre-allocated and zeroed-out VM disk image by using -server/storage off-loads. - -### Scope - -Nature of proposed change -------------------------- - -An FOP supported in libgfapi and FUSE. - -Implications on manageability ------------------------------ - -None. - -Implications on presentation layer ----------------------------------- - -N/A - -Implications on persistence layer ---------------------------------- - -N/A - -Implications on 'GlusterFS' backend ------------------------------------ - -N/A - -Modification to GlusterFS metadata ----------------------------------- - -N/A - -Implications on 'glusterd' --------------------------- - -N/A - -How To Test ------------ - -Test server offload by measuring the time taken for creating a fully -allocated and zeroed file on Posix backend. - -Test storage offload by measuring the time taken for creating a fully -allocated and zeroed file on BD backend. - -User Experience ---------------- - -Fast provisioning of VM images when GlusterFS is used as a file system -backend for KVM virtualization. - -Dependencies ------------- - -zerofill() support in BD backend depends on the new BD translator - -<http://review.gluster.org/#/c/4809/> - -Documentation -------------- - -This feature add support for a new ZEROFILL fop. Zerofill writes zeroes -to a file in the specified range. This fop will be useful when a whole -file needs to be initialized with zero (could be useful for zero filled -VM disk image provisioning or during scrubbing of VM disk images). - -Client/application can issue this FOP for zeroing out. Gluster server -will zero out required range of bytes ie server offloaded zeroing. In -the absence of this fop, client/application has to repetitively issue -write (zero) fop to the server, which is very inefficient method because -of the overheads involved in RPC calls and acknowledgements. - -WRITESAME is a SCSI T10 command that takes a block of data as input and -writes the same data to other blocks and this write is handled -completely within the storage and hence is known as offload . Linux ,now -has support for SCSI WRITESAME command which is exposed to the user in -the form of BLKZEROOUT ioctl. BD Xlator can exploit BLKZEROOUT ioctl to -implement this fop. Thus zeroing out operations can be completely -offloaded to the storage device , making it highly efficient. - -The fop takes two arguments offset and size. It zeroes out 'size' number -of bytes in an opened file starting from 'offset' position. - -This feature adds zerofill support to the following areas: - -- libglusterfs -- io-stats -- performance/md-cache,open-behind -- quota -- cluster/afr,dht,stripe -- rpc/xdr -- protocol/client,server -- io-threads -- marker -- storage/posix -- libgfapi - -Client applications can exploit this fop by using glfs\_zerofill -introduced in libgfapi.FUSE support to this fop has not been added as -there is no system call for this fop. - -Here is a performance comparison of server offloaded zeofill vs zeroing -out using repeated writes. - - [root@llmvm02 remote]# time ./offloaded aakash-test log 20 - - real 3m34.155s - user 0m0.018s - sys 0m0.040s - - - [root@llmvm02 remote]# time ./manually aakash-test log 20 - - real 4m23.043s - user 0m2.197s - sys 0m14.457s - [root@llmvm02 remote]# time ./offloaded aakash-test log 25; - - real 4m28.363s - user 0m0.021s - sys 0m0.025s - [root@llmvm02 remote]# time ./manually aakash-test log 25 - - real 5m34.278s - user 0m2.957s - sys 0m18.808s - -The argument log is a file which we want to set for logging purpose and -the third argument is size in GB . - -As we can see there is a performance improvement of around 20% with this -fop. - -Status ------- - -Patch : <http://review.gluster.org/5327> Status : Merged
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