Comments on: NILFS: A File System to Make SSDs Scream http://www.linux-mag.com/id/7345/ Open Source, Open Standards Sat, 05 Oct 2013 13:48:18 +0000 hourly 1 http://wordpress.org/?v=3.1 By: Isabel http://www.linux-mag.com/id/7345/#comment-1055775 Isabel Sun, 14 Jul 2013 07:07:35 +0000 http://www.linux-mag.com/id/7345/#comment-1055775 You actually make it seem so easy with your presentation but I to find this matter to be really one thing that I think I would never understand. It sort of feels too complex and very broad for me. I am looking ahead to your subsequent submit, I'll try to get the cling of it! You actually make it seem so easy with your presentation but I to find this matter to be really one thing that I think I would never understand. It sort of feels too complex and very broad for me. I am looking ahead to your subsequent submit, I’ll try to get the cling of it!

]]> By: Ute http://www.linux-mag.com/id/7345/#comment-988671 Ute Sat, 08 Jun 2013 08:54:35 +0000 http://www.linux-mag.com/id/7345/#comment-988671 Why viewers still make use of to read news papers when in this technological world the whole thing is available on web? Why viewers still make use of to read news papers when in this technological world the whole thing is available on web?

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]]> By: jrichter http://www.linux-mag.com/id/7345/#comment-6476 jrichter Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6476 Performance is great, but in my experience, as large an issue can be the difficulty of expanding the file systems and underlying disk structure. Easing that task is a characteristic of, for example, ZFS. Does NILFS have any features in this area? Performance is great, but in my experience, as large an issue can be the difficulty of expanding the file systems and underlying disk structure. Easing that task is a characteristic of, for example, ZFS. Does NILFS have any features in this area?

]]> By: fbacchella http://www.linux-mag.com/id/7345/#comment-6477 fbacchella Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6477 "In contrast, other file systems such as ZFS, can provide snapshots but they have to suspend operation to perform the snapshot operation."<br /> " creating these checkpoints or snapshots do not result in decreased performance as they do for file systems such as ZFS."<br /> <br /> That's plain FUD. Snapshots are free operations (except for the disk space of course) in zfs and as no impact on performance. “In contrast, other file systems such as ZFS, can provide snapshots but they have to suspend operation to perform the snapshot operation.”
” creating these checkpoints or snapshots do not result in decreased performance as they do for file systems such as ZFS.”

That’s plain FUD. Snapshots are free operations (except for the disk space of course) in zfs and as no impact on performance.

]]> By: rejoc http://www.linux-mag.com/id/7345/#comment-6478 rejoc Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6478 On OpenVMS, 10++ years ago, there was such a FS called Spiralog !<br /> <br /> Write performance was tremendous !<br /> <br /> But also, it is the only filesystem I've seen where, when the disk was full, you could not delete any file because deleting a file added a new record to the log and there was no more place on the disk to extend the log :) On OpenVMS, 10++ years ago, there was such a FS called Spiralog !

Write performance was tremendous !

But also, it is the only filesystem I’ve seen where, when the disk was full, you could not delete any file because deleting a file added a new record to the log and there was no more place on the disk to extend the log :)

]]> By: mrbig4545 http://www.linux-mag.com/id/7345/#comment-6479 mrbig4545 Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6479 I registered just to say, you don't want raid in the filesystem, it breaks the whole layered design thing. on top of that, software raid in linux is one of the finest in existence, no harm using it underneath NILFS (which looks pretty awesome btw) to achieve the same thing, in a more modular fashion. I registered just to say, you don’t want raid in the filesystem, it breaks the whole layered design thing. on top of that, software raid in linux is one of the finest in existence, no harm using it underneath NILFS (which looks pretty awesome btw) to achieve the same thing, in a more modular fashion.

]]> By: momokuri http://www.linux-mag.com/id/7345/#comment-6480 momokuri Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6480 NILFS seems not having the feature to expand volume, but one of developers said they have experimental code in his test repository. <br /> https://www.nilfs.org/pipermail/users-ja/2008-November/000059.html<br /> (in Japanese)<br /> <br /> I think it will be apear after merging it into mainline kernel, maybe 2.6.32 or later. NILFS seems not having the feature to expand volume, but one of developers said they have experimental code in his test repository.
https://www.nilfs.org/pipermail/users-ja/2008-November/000059.html
(in Japanese)

I think it will be apear after merging it into mainline kernel, maybe 2.6.32 or later.

]]> By: ddebroy http://www.linux-mag.com/id/7345/#comment-6481 ddebroy Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6481 I get why a log structured file system, which is meant to optimize for a rotating disk head, is beneficial for rotating disks. I don't get how that translates to "make your SSDs scream". Since SSDs don't have spinning disks, how does a log structured file system boost a SSD? Infact, doesn't the fact that a FS is log-structured make it completely SSD-unaware and therefore inferior to a file system that is not log structured (say allocates data in some random fashion all over the volume)? <br /> <br /> The main design principle for this file system appears to be optimizing for a premise (i.e. a rotating head) which is completely absent in the case of a SSD. I get why a log structured file system, which is meant to optimize for a rotating disk head, is beneficial for rotating disks. I don’t get how that translates to “make your SSDs scream”. Since SSDs don’t have spinning disks, how does a log structured file system boost a SSD? Infact, doesn’t the fact that a FS is log-structured make it completely SSD-unaware and therefore inferior to a file system that is not log structured (say allocates data in some random fashion all over the volume)?

The main design principle for this file system appears to be optimizing for a premise (i.e. a rotating head) which is completely absent in the case of a SSD.

]]> By: golding http://www.linux-mag.com/id/7345/#comment-6482 golding Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6482 Wonder what Jörn Engel (dev of LogFS) thinks of this.<br /> Does this include his efforts? Wonder what Jörn Engel (dev of LogFS) thinks of this.
Does this include his efforts?

]]> By: laytonjb http://www.linux-mag.com/id/7345/#comment-6483 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6483 In general, I agree with you. But a very large number of people are asking for RAID to be included in the file system ala' ZFS. I'm not a file system designer enough to be able to explain the details of either approach. But when looking at btrfs, I found that I like the built-in RAID because it was easier to build the file system. It may have been being lazy :) or it may have been mounting and unmounting the file system so much, but I did like it better. In general, I agree with you. But a very large number of people are asking for RAID to be included in the file system ala’ ZFS. I’m not a file system designer enough to be able to explain the details of either approach. But when looking at btrfs, I found that I like the built-in RAID because it was easier to build the file system. It may have been being lazy :) or it may have been mounting and unmounting the file system so much, but I did like it better.

]]> By: laytonjb http://www.linux-mag.com/id/7345/#comment-6484 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6484 I would recommend reading the NILFS mailing list archives and perhaps some of the other articles around.<br /> <br /> From my understanding one of the things that a log-structured file system gives you is that thing are just appended to the head of the log. Then garbage collection clean up later. SSD's have notoriously bad rewrite performance because you have to actually go in and change the cells before you can write to them again. This means you have to basically do two writes. Of course, SSD drive manufacturers are figuring out ways around this or to at least hide it. With log-structured file systems recovering space can happen when there is no pressure to reuse the particular space of the SSD.<br /> <br /> Plus the "blocks" (if you will) of the SSD that get erased are fairly large. So it's definitely possible for a classic file system to "re-erase" a section of the drive several times even if it's already been erased. Log-structured file systems can be "tuned" to erase or reclaim space that<br /> matches the size that needs to be erased. Consequently you only do this one time. BTW - classic file systems are gaining this behavior as well (I think btrfs does this and I would be willing to bet that ZFS does as well but I don't know for sure).<br /> <br /> Jeff I would recommend reading the NILFS mailing list archives and perhaps some of the other articles around.

From my understanding one of the things that a log-structured file system gives you is that thing are just appended to the head of the log. Then garbage collection clean up later. SSD’s have notoriously bad rewrite performance because you have to actually go in and change the cells before you can write to them again. This means you have to basically do two writes. Of course, SSD drive manufacturers are figuring out ways around this or to at least hide it. With log-structured file systems recovering space can happen when there is no pressure to reuse the particular space of the SSD.

Plus the “blocks” (if you will) of the SSD that get erased are fairly large. So it’s definitely possible for a classic file system to “re-erase” a section of the drive several times even if it’s already been erased. Log-structured file systems can be “tuned” to erase or reclaim space that
matches the size that needs to be erased. Consequently you only do this one time. BTW – classic file systems are gaining this behavior as well (I think btrfs does this and I would be willing to bet that ZFS does as well but I don’t know for sure).

Jeff

]]> By: laytonjb http://www.linux-mag.com/id/7345/#comment-6485 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6485 Thanks for comment about this - I had not seen that yet.<br /> <br /> If you think about, expanding or even shrinking a lob based file system should be fairly easy. If you add more space, you just have to make the log aware of that space. If you shrink the file system, I think you can do the same thing but in reverse.<br /> <br /> Of course the devil is in the details :) And I don't know the details.<br /> <br /> Jeff Thanks for comment about this – I had not seen that yet.

If you think about, expanding or even shrinking a lob based file system should be fairly easy. If you add more space, you just have to make the log aware of that space. If you shrink the file system, I think you can do the same thing but in reverse.

Of course the devil is in the details :) And I don’t know the details.

Jeff

]]> By: laytonjb http://www.linux-mag.com/id/7345/#comment-6486 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7345/#comment-6486 I did find an article that might help you in your quest for understanding why log-structured file systems make SSD's scream:<br /> <br /> http://www.ibm.com/developerworks/linux/library/l-flash-filesystems/<br /> <br /> I hope this helps (but I haven't read the whole thing).<br /> <br /> Jeff I did find an article that might help you in your quest for understanding why log-structured file systems make SSD’s scream:

http://www.ibm.com/developerworks/linux/library/l-flash-filesystems/

I hope this helps (but I haven’t read the whole thing).

Jeff

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