Re: [CentOS] VDO killed my server
Interesting observation! I'm thinking about trying VDO too. On 09/03/2018 11:40 AM, david wrote: I was impressed with the description of VDO (Virtual Device Optimizer?) in the RedHat documentaion, so much that I tried to use it. The tutorials led me to a few commands. I built a VDO device on top of two USB disks which I made into a Logical Volume, and I was ready to go. USB connections are notorious flimsy. They are prone to randomly dropping ops and silent intermittent connection breaks, and are known to cause a lot of hard-to-debug problems when being used with more complex filesystems, such as ZFS and btrfs. Of course we shouldn't blame USB for every problem, but I wouldn't be surprised if USB is playing naughty here. In my test case, I had a file set of about 600 GB. There was 5 TB of space between the two disk LVMs. So, I thought, let's see if I can activate deduplication and compression, and see if VDO can take two, or three, or four identical copies of that file set, at different points in the file system tree. Needless to say, all worked well with the first set. It took 24 hours to copy. The second set took another 24 hours, and all seemed well. As I was copying the third set, I started to observe some problems. The computer was serving other functions (internal DHCPD, DNS, internal HTTPD), and these started to fail. There were no obvious alerts or warnings from VDO, but the other functions of the system started to die. The diagnostics from JOURNALCTL were vague (failure to create a file...), Did these failures to create a file occur only on the file system on VDO or also on other file system? but when I want looking with 'df', all the file systems seemed to have enough room for everything. Even the 'top' program showed available space in the pools it revealed. How about free memory? What did `free -m` say? After hours of my internal clients complaining, I finally removed the 'mount' in /etc/fstab that loaded the VDO system, killed the file copies, and rebooted. The system then resumed normal healthy functions, but without the VDO files. It my mind, there are a few points: - If VDO is competing for a finite resource (Memory?), it probably should start posting warnings, and eventually rejecting new files when the pool is nearly full. Or maybe, use a pool other than what the other services use so as to minimize the impact on them. Definitely. - The documentation talks about 'tuning', but if this resource is one of concern, please don't bury it in the footnotes to the appendix. I agree. Tuning should only affect performance, never normal functionality. -- Yan Li ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
[CentOS] VDO killed my server
Folks I was impressed with the description of VDO (Virtual Device Optimizer?) in the RedHat documentaion, so much that I tried to use it. The tutorials led me to a few commands. I built a VDO device on top of two USB disks which I made into a Logical Volume, and I was ready to go. In my test case, I had a file set of about 600 GB. There was 5 TB of space between the two disk LVMs. So, I thought, let's see if I can activate deduplication and compression, and see if VDO can take two, or three, or four identical copies of that file set, at different points in the file system tree. Needless to say, all worked well with the first set. It took 24 hours to copy. The second set took another 24 hours, and all seemed well. As I was copying the third set, I started to observe some problems. The computer was serving other functions (internal DHCPD, DNS, internal HTTPD), and these started to fail. There were no obvious alerts or warnings from VDO, but the other functions of the system started to die. The diagnostics from JOURNALCTL were vague (failure to create a file...), but when I want looking with 'df', all the file systems seemed to have enough room for everything. Even the 'top' program showed available space in the pools it revealed. After hours of my internal clients complaining, I finally removed the 'mount' in /etc/fstab that loaded the VDO system, killed the file copies, and rebooted. The system then resumed normal healthy functions, but without the VDO files. It my mind, there are a few points: - If VDO is competing for a finite resource (Memory?), it probably should start posting warnings, and eventually rejecting new files when the pool is nearly full. Or maybe, use a pool other than what the other services use so as to minimize the impact on them. - The documentation talks about 'tuning', but if this resource is one of concern, please don't bury it in the footnotes to the appendix. - Using VDO on top of LVM seems to be the logical way to use deduplication for a large file set, yet the use cases don't seem to cover this (unless I misread them) I have reverted back reluctantly to using ZFS for this function. Have others had issues with VDO? David Kurn Linux amateur ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] OT: Linux recommendations for old Pentium PC
On Monday 03 September 2018 15:13:06 Yves Bellefeuille wrote: > This means that you'll need a 32-bit OS, and that PAE might not be > recognized by the OS. Debian 9 32-bit would work; CentOS 6 32-bit > might not. It previously had Centos 6 on it, but I wanted to avoid that as it now has a limited shelf life. However, when I tried lubuntu the Bacula versions were not compatible. Now Putting Centos 6 32-bit back on and crossing my fingers. I'm really impessed that the m/board recognised the 4TB drive ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] OT: Linux recommendations for old Pentium PC
Gary Stainburn wrote: > I had not considered the lack of energy efficiency. The server has > a MSI MS-9628 board with a Pentium M processor, and the one modern > 4TB HDD. This means that you'll need a 32-bit OS, and that PAE might not be recognized by the OS. Debian 9 32-bit would work; CentOS 6 32-bit might not. -- Yves Bellefeuille ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
[CentOS] Centos on Dell XPS15
Is anyone successfully running Centos 7 on a Dell XPS15? If so, which model? If not, what was the problem? Thank you! ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] OT: Linux recommendations for old Pentium PC
On Sep 3, 2018, at 2:30 AM, Gary Stainburn wrote: > > ...Pentium M processor...tiny fan...assumed power consumption would be low. You could well be right, but I’m a fan of taking measurements over guessing. :) If you were in the US, I’d recommend either of these from personal testing: https://amzn.to/2NMWXJq https://amzn.to/2oyz5Oz I wrote the review voted most helpful for the latter item. You might want to read it. A clamp meter + line splitter is more fiddly to use than a Kill-a-Watt, but you can use the clamp meter for many more things, so it’s a better overall value unless you simply will not be doing those other things. Neither of those will work for you due to US vs UK AC line connector differences, but these two items appear to be roughly equivalent: https://www.amazon.co.uk/dp/B01DSQ30FO/ https://www.amazon.co.uk/dp/B00H99EECU/ plus: https://www.amazon.co.uk/dp/B075D512KM/ I’ve found the same clamp meter that I reviewed above, differing only in OEM labeling. I’m not too happy with my guess for the best line splitter, for two reasons: First, I'm unfamiliar with your UK power plugs, so I don’t know if that’s actually a UK plug. Second, two of the reviews of that line splitter point out a design flaw that you might care about. I’d have passed it by if I could find something better on the Amazon.co.uk site, but that is the best I found, alas. You need a line splitter to do this test with a clamp meter, else you get a zero reading since the electromagnetic field from the neutral line cancels that of the hot line: you have to measure one or the other, separately. It doesn’t matter which one you measure: the current through both lines is the same, differing only in direction, which is what we mean when we call something an electrical “circuit”. Alternate plan: build a “broken circuit:” https://tangentsoft.com/elec/broken-circuit.html You can either make one for an inline current meter, as shown, or take the basic idea to DIY your own line splitter. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] OT: Linux recommendations for old Pentium PC
On Friday 31 August 2018 18:20:20 Warren Young wrote: > You’re giving two very mixed signals here. > > “Old Pentium,” as someone else said, can mean anything back to 1993, but “4 > TB drive” suggests something far newer than that. > > I ask because that affects the expected energy draw of the server. If it’s > old, it could be 200 W or so. If you’re using “old” rather loosely, then > it could be down in the double digits. > > Here’s why it matters: > >https://www.rapidtables.com/calc/electric/energy-cost-calculator.html > > At 12 pence per kWh — typical for power in some places in your country, > based on your TLD — it’s going to cost you about 1 pound per watt consumed > if it runs all day every day. If it draws 35 W, that’s £35/yr. If it > draws 200 W, that’s £200/yr. Hi Warren, I had considered power consumption but only with regard that it is a small footprint system, both physically and in terms of processing power etc. I had not considered the lack of energy efficiency. The server has a MSI MS-9628 board with a Pentium M processor, and the one modern 4TB HDD. There is one tiny fan in the PSU and another tiny processor fan on the CPU. From this I (possibly wrongly) assumed power consumption would be low. It used to have 2 x 1.5TB drivers with software RAID until that died. I am still in the process of installing lubuntu so I don't know how effective it will be. I had considered putting Centos6 32-bit back on, but has been said elsewhere that's very near EOL. Having said that, some of my (soon to be replaced) SAMBA boxes are still runnning F9. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] OT: Linux recommendations for old Pentium PC
On Friday 31 August 2018 18:09:13 Leon Fauster via CentOS wrote: > We use mysql as database backend for bacula, and it becomes heavy loaded, > over time especially wenn restoring respectively generating filelists. So, > not sure if such old CPU provides enough compute power ... This isn't the director, it's just a remote storeage device. All it has to do is talk network and HDD. Why is why I've retained it as it's a 1U half depth rack server and fits into my already overcrowded cabinet. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
