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Reclaim free space broken in 7.0


Florin Baca

Question

We have 3 XenServers in our infra, the oldest one running a fresh install of 6.5, newest running a fresh install of 7.0 and one which I have upgraded yesterday from 6.5 to 7.0. There were no upgrade issues, aside from guest tools not installing on Windows hosts. Storage is local on all servers.

 

Cleaning the upgraded server, I tried to 'reclaim free storage' which failed with:

 

blkdiscard: /dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv: BLKDISCARD ioctl failed: Operation not supported

 

I looked in SMlog and I can see the blkdiscard runs after the lvcreate command:

 

Sep  5 07:20:57 xen2 SM: [11766] do_trim: {'sr_uuid': '54fcd1f8-ef26-d32f-1a18-db9e16169231'}
Sep  5 07:20:57 xen2 SM: [11766] lock: opening lock file /var/lock/sm/54fcd1f8-ef26-d32f-1a18-db9e16169231/sr
Sep  5 07:20:57 xen2 SM: [11766] lock: tried lock /var/lock/sm/54fcd1f8-ef26-d32f-1a18-db9e16169231/sr, acquired: True (exists: True)
Sep  5 07:20:57 xen2 SM: [11766] ['/sbin/lvs', '--noheadings', '/dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv']
Sep  5 07:20:57 xen2 SM: [11766] FAILED in util.pread: (rc 5) stdout: '', stderr: '  Failed to find logical volume "VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv"
Sep  5 07:20:57 xen2 SM: [11766] '
Sep  5 07:20:57 xen2 SM: [11766] Ignoring exception for LV check: /dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv !
Sep  5 07:20:57 xen2 SM: [11766] ['/sbin/lvcreate', '-n', '54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv', '-l', '100%F', 'VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231']
Sep  5 07:20:58 xen2 SM: [11766]   pread SUCCESS
Sep  5 07:20:58 xen2 SM: [11766] ['/usr/sbin/blkdiscard', '-v', '/dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv']
Sep  5 07:20:58 xen2 SM: [11766] FAILED in util.pread: (rc 1) stdout: '', stderr: 'blkdiscard: /dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv: BLKDISCARD ioctl failed: Operation not supported
Sep  5 07:20:58 xen2 SM: [11766] '
Sep  5 07:20:58 xen2 SM: [11766] ['/sbin/lvs', '--noheadings', '/dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv']
Sep  5 07:20:58 xen2 SM: [11766]   pread SUCCESS
Sep  5 07:20:58 xen2 SM: [11766] ['/sbin/lvremove', '-f', '/dev/VG_XenStorage-54fcd1f8-ef26-d32f-1a18-db9e16169231/54fcd1f8-ef26-d32f-1a18-db9e16169231_trim_lv']
Sep  5 07:20:58 xen2 SM: [11766]   pread SUCCESS
Sep  5 07:20:58 xen2 SM: [11766] ['/sbin/dmsetup', 'status', 'VG_XenStorage--54fcd1f8--ef26--d32f--1a18--db9e16169231-54fcd1f8--ef26--d32f--1a18--db9e16169231_trim_lv']

 

For testing, I ran the same on the freshly installed XenServer 7.0 but I am seeing the exact same error so it's not caused by the upgrade. I don't know if this can be ignored (since it shows in XenCenter as well) but the virtual allocation reported by XenCenter is larger than the actual size of the disk.

 

As a reference, I also reclaimed the free space on the old 6.5 server. The operation succeeds and there is no blkdiscard command in the SMlog.

 

Has anyone else seen these issues with 7.0?

 

Thanks,

Florin

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The error talked about has to do with SSD drives since currently there is no TRIM support built into any version of XenServer. TRIM is the means by which SSD drive blocks can be marked as not containing any valid data and can be reused. I have not heard of any specific plans to support TRIM. The article discusses only the error message reporting, not introducing TRIM support.

 

-=Tobias

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Hi All,

 

I have a SSD RAID and did not have this problem on 6.5, but do with 7.x. If I am understanding this correctly, XenServer is not built for SSDs (no TRIM), nor are there any plans to, and one needs to completely reformat their XenServers to 'fix' the space issue, but this is only a temporary fix as XenServer will not reclaim disk space on SSDs.

 

Thanks

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On 17/12/2017 at 2:50 PM, Tobias Kreidl said:

The error talked about has to do with SSD drives since currently there is no TRIM support built into any version of XenServer. TRIM is the means by which SSD drive blocks can be marked as not containing any valid data and can be reused. I have not heard of any specific plans to support TRIM. The article discusses only the error message reporting, not introducing TRIM support.

 

-=Tobias

But I see this TRIM error and I use only SAS HDs. The same hardware with XenServer 6.5 does not display such an error.

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2 hours ago, Jason Rasmussen said:

Hi All,

 

I have a SSD RAID and did not have this problem on 6.5, but do with 7.x. If I am understanding this correctly, XenServer is not built for SSDs (no TRIM), nor are there any plans to, and one needs to completely reformat their XenServers to 'fix' the space issue, but this is only a temporary fix as XenServer will not reclaim disk space on SSDs.

 

Thanks

 

Hello,

 

I use only SATA and SAS disks on all my servers and I see this error in XenServer 7.2 ... While it works perfectly in XenServer 6.5

I have this problem on a Dell server with SAS disks and on an HP server with SATA disks

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