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Linux geek

Apr
23
comment What is RAID5 + Hotspare?
For a specific example, HP smartarray 6400 controllers rebuilds the array again after the failed drive is replaced. Probably other smartarray controllers as well, as they probably all use more or less the same firmware.
Apr
13
comment May the file size returned by stat be compromised?
Well, 'ls -l' does a lstat() syscall, as does 'du' and the 'stat' command-line tool. The difference is just which field(s) they read from the stat struct the syscall returns.
Apr
8
comment How does NFS read cache work on Debian?
Yes, the client caches file content in the page cache, just like it does for a local filesystem. The attributes are used to decide if and when the cached file contents are invalidated.
Apr
1
comment Why do Linux networks use Samba?
/etc/exports supports cidr or netmask notation, so for the common case of exporting to a contiguous block there is no need to list every client explicitly. Also, wrt. the symlinking, see samba.org/samba/news/symlink_attack.html
Jan
8
comment cause for high Interrupts and context switches
To be pedantic, entering the kernel is only needed when the lock is contended, or when waking up waiting tasks. See en.wikipedia.org/wiki/Futex
Jan
3
comment Does HTTPS use TCP or UDP?
Or if the packets arrive out of order, as UDP contains no provisions for reordering packets like TCP.
Dec
28
comment Centralized accounts and multiple logins
@Jim B - POSIX locks are advisory, so there's no difference between NFS and local fs locking in that respect.
Dec
23
comment Splitting a shared pool of disks in a SAN into numerous LUNS
@Chopper3: FWIW, we haven't had any reliability issues with FATA disks. But yeah, they're big and slow so rebuilding takes time; VRAID6 helps me sleep at night.
Dec
23
comment Splitting a shared pool of disks in a SAN into numerous LUNS
@sysadmin1138 Yeah as a rule of thumb you should avoid having disks with wildly different performance or capacity in the same disk group. In practice we tend to have all FC disks in one group and all FATA disks in another. There is some capacity and potentially performance loss from having different capacity disks in the same group (when we expand new disks are often bigger), but OTOH as Chopper3 said there is a benefit from having as few DG's as possible, so it's a compromise.
Dec
23
comment Splitting a shared pool of disks in a SAN into numerous LUNS
I'm not sure where you're actually disagreeing with ynguldyn? The question was whether to have a single LUN (~vdisk) or multiple LUN's on the same pool (~disk group). And ynguldyn says there's no performance difference, which is correct. Also, to be pedantic, EVA's don't have hot standby disks, they use distributed sparing.
Dec
2
comment 64bit UnixODBC and FreeTDS: a bug in libtdsodbc.so?
You're right, blaming php-odbc is premature at this point; it might be there or it might not. The bug could also be in the odbc-tds bridge as you mention, but not necessarily. It might be that php-odbc stores a pointer into an 32-bit integer (this was the reason for the problem I reported to Redhat), but it bombs out only when it gets to the odbc-tds bridge. Also, see my edited reply for a possible workaround that unfortunately requires some programming effort on your effort to convert to PDO.
Oct
22
comment Are Extended Validation SSL certificates effective?
+1 Just like the rest of the CA business, the EV thing is a ripoff.
Jun
28
comment How to find out all the software packages installed by default on a linux install?
Useless use of cat detected; you can do just 'dpkg --set-selections < installedpackages.txt' ;)
Jun
28
comment How to find out all the software packages installed by default on a linux install?
dpkg -l doesn't need superuser access.