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physical space taken by a file on a NetApp
How can I determine the physical amount of space taken by a file on a
NetApp (WAFL)? |
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physical space taken by a file on a NetApp
On Tue, 10 Jul 2007 11:51:44 -0700, wrote:
How can I determine the physical amount of space taken by a file on a NetApp (WAFL)? Divide the 'du' output by 4k (block size)? Unless you have some weird file size or layout I would think a simple 'du' would work just fine. Not sure how it would work in windows, sorry. ~F |
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physical space taken by a file on a NetApp
On Jul 11, 2:55 am, Faeandar wrote:
On Tue, 10 Jul 2007 11:51:44 -0700, wrote: How can I determine the physical amount of space taken by a file on a NetApp (WAFL)? Divide the 'du' output by 4k (block size)? Unless you have some weird file size or layout I would think a simple 'du' would work just fine. Not sure how it would work in windows, sorry. ~F Why are you dividing by 4. I feel if you give #du -sk Dir It should give size in KB consumed bye dir. and it shouldn't concern with WAFL which have 4k block size. du will send request to NetApp which will provide size to du and du will provide to user. Can you comment on it and can explain your view ? Raju |
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physical space taken by a file on a NetApp
I'll take a stab at it...
By physical I'm assuming you mean actual sectors on physical media? So if this is the case it depends on the following factors that I'm aware of. 1) WAFL overhead each aggregate needs 10% for WAFL overhead, you could consider this as using additional physical space. 2) Right-sizing Drives are right-sized to account for minor deviations in total storage capacity among hard-drive vendors. I.E. All "146GB" drives are sized to a certain number to make things clean/safe from a RAID config perspective. You loose a marginal amount of storage from each drive due to this. (I'm not sure of the amount) 3) Aggregate/RAID Configuration Depending on the disk layout differing amounts of physical space will be consumed. Assume an Aggregate with raidsize set at 9 with RAID-DP with 18 total drives. So the amount of physical space consumed would be an additional ~22% (2/9) so a 1MB file would consume 1.22MB of physical space due to RAID overhead. 4) Checksums If using a V-series block checksums consume an additional *12.5%* from each physical disk. This is obviously a big hit, zoned checksums consume only a marginal amount of space, but block is the recommendation. This consumes additional physical space as well. Note this is only with a V-series. 5) Snap reserve Aggregate and Volume snap reserves should probably also be calculated if you have snapshots turned on just to give a true view of amount of space required, even though this physical space isn't needed until a snap is taken, and I overwrite those blocks from the production filesystem. Also dont forget to convert the marketing number to real usable gigabytes etc... I.E. a drive advertised as a "146GB" drive really means there are roughly 146,000,000,000 bytes available. 146,000,000,000/1000/1000/1000 = 146 Gigabytes. However the computer doesn't use decimal and the division should be by 2^10 (which is 1024) so a "146GB" drive is really 146,000,000,000/1024/1024/1024 =~ 136GB As for the 4k block size of WAFL, I dont think that has an impact really on files that are stored, meaning, if I store a 1k file it doesnt take 4k minimum. However if I increase/decrease the size of my flexvol I have to do it in 4k increments. Thats all I can think of! Please add or correct if necessary! -Anthony Raju Mahala wrote: On Jul 11, 2:55 am, Faeandar wrote: On Tue, 10 Jul 2007 11:51:44 -0700, wrote: How can I determine the physical amount of space taken by a file on a NetApp (WAFL)? Divide the 'du' output by 4k (block size)? Unless you have some weird file size or layout I would think a simple 'du' would work just fine. Not sure how it would work in windows, sorry. ~F Why are you dividing by 4. I feel if you give #du -sk Dir It should give size in KB consumed bye dir. and it shouldn't concern with WAFL which have 4k block size. du will send request to NetApp which will provide size to du and du will provide to user. Can you comment on it and can explain your view ? Raju |
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